Компоненты среды выполнения Windows Windows Runtime components

Компонент среды выполнения Windows — это автономный программный модуль, который можно создать и использовать в качестве источника информации на любом языке среды Windows, включая C#, C++/WinRT, Visual Basic, JavaScript и C++/CX. A Windows Runtime component is a self-contained software module that you can author, reference, and use with any Windows Runtime language (including C#, C++/WinRT, Visual Basic, JavaScript, and C++/CX). Вы можете создать компонент среды выполнения Windows с помощью Visual Studio, а затем использовать его в приложении универсальной платформы Windows (UWP). You can use Visual Studio to create a Windows Runtime component that can be used in your Universal Windows Platform (UWP) app.

Для разработчиков C++ мы рекомендуем использовать C++/WinRT. For C++ developers, we recommend that you use C++/WinRT for new applications. C++/WinRT — это полностью стандартная проекция языка C++17 для API среды выполнения Windows (WinRT), реализованная как библиотека на основе файлов заголовков и предназначенная для предоставления вам первоклассного доступа к современным интерфейсам API Windows. C++/WinRT is an entirely standard modern C++17 language projection for Windows Runtime (WinRT) APIs, implemented as a header-file-based library, and designed to provide you with first-class access to the modern Windows API. Сведения о создании компонента среды выполнения Windows с помощью C++/WinRT см. в статье Создание компонентов среды выполнения Windows с помощью C++/WinRT. To learn how to create a Windows Runtime component using C++/WinRT, see Windows Runtime components with C++/WinRT.

Включение и отключение компонентов Windows 10

Как известно, Windows 10 отличается набором компонентов от предыдущих версий операционных систем Windows. Зачастую требуется их включить или выключить, чтобы они не потребляли системные ресурсы, да и просто не мешали. В этой статье мы рассмотрим как это сделать быстрее и эффективнее.

Начнем с того, что существует два основных способа работы с компонентами (они еще называются features) — утилита DISM и командлеты Powershell. И то и другое встроено в Windows 10, в отличие от Windows 7, где dism можно было добавить или установив пакет Windows ADK, или руками скопировав dism.exe с другого компьютера.

Сразу отмечу, что утилиту dism и среду powershell для работы с системой необходимо запускать от имени администратора, даже если ваш аккаунт уже находится в группе локальных админов. Итак, вы или находите cmd или windows powershell в меню и, кликнув правой кнопкой мышки, выбираете «Запуск от имени администратора».

В Windows 10 есть понятие Features и Capabilities. Первое — это привычные нам компоненты, которые можно найти в Панели управления -> Программы и компоненты -> Включение и отключение компонентов Windows. То есть это встраиваемые модули, которые выполняют определенный сервисный функционал.

Capabilities — это дополнительные возможности, которые расширяют возможности интерфейса и увеличивают удобство пользователя. Среди них — Language packs, наборы шрифтов. Да, Microsoft удалил часть нестандартных шрифтов, которые теперь вынесены в опциональные компоненты. Скачать эти компоненты можно в виде ISO файла с сайта Volume Licensing Service Center или напрямую через Internet и графический интерфейс Windows. Такую концепцию Microsoft назвала Features on Demand (FOD). Их в более ранних версия Windows не было.

Работаем с Windows Features

Итак, список установленных компонентов можно посмотреть командой

Dism /online /Get-Features

Вот как в Powershell можно получить список всех компонентов командлетами Get-WindowsFeature (для Windows Server) или Get-WindowsOptionalFeature (Windows 10):

Чтобы получить список отключенных компонентов, введите:

Get-WindowsOptionalFeature -Online | ? state -eq ‘disabled’ | select featurename

Этот список также можно вывести в файл (для windows Server):

Get-WindowsFeature | Where-Object <$_.Installed -match “True”>| Select-Object -Property Name | Out-File C:\Temp\WindowsFeatures.txt

Посмотрев список названий и их состояние, можно использовать эти названия для того, чтобы компоненты включить или выключить:

Dism /online /Enable-Feature /FeatureName:TFTP /All

ключ /All позволяет включить также все дочерние компоненты;

Установка компонентов через Powershell выполняется командой Enable-WindowsOptionalFeature.

Enable-WindowsOptionalFeature -Online -FeatureName RSATClient-Roles-AD-Powershell

Параметр -All включает все дочерние компоненты.

Dism /online /Disable-Feature /FeatureName:TFTP

Аналогично, через Powershell это можно сделать командой Disable-Windowsoptionalfeature -online -featureName [feature name].

Обратите внимание, некоторые фичи имеют разные названия в Windows 7 и Windows 10. Например, RSAT в Windows 7 — это RemoteServerAdministrationTools, а в Windows 10 — RSATclient.

Управление Features on Demand (FOD)

Если вы устанавливаете их через графический интерфейс, то вам необходимо пройти “System –> App & features –> Manage optional features” и нажать знак + напротив необходимых компонентов.

Чтобы сделать это автоматизированно через командную строку, наберите чтобы получить список доступных компонентов:

DISM.EXE /Online /Get-Capabilities

или на Powershell:

Как и прежде, запомните название необходимых вам компонентов, чтобы включить их командой (на примере .Net Framework 3):

DISM.EXE /Online /Add-Capability /CapabilityName:NetFx3

или на Powershell:

Add-WindowsCapability –Online -Name NetFx3

Если же у вас нет доступа в Интернет, то есть выход. Итак, вы скачиваете ISO образ диска с FOD компонентами с сайта Volume Licensing Service Center. Файлы будут разные для разных релизов Windows 10 — 1511, 1607, 1703, 1709. Важно помнить, что компоненты одного релиза не подходят к другому. Если вы сделаете in-place upgrade (установка одного релиза поверх другого через обновление), то несовместимые установленные компоненты будут удалены без вашего желания! Да, Microsoft удаляет то, что считает несовместимым при обновлении.

Так вот, ISO файл содержит набор неизвестных и сложных для понимания файлов с расширением cab. Вот чудесный файлик на сайта Microsoft, который обясняет назначение каждого файла. Итак, существуют следующие типы FOD:

• Microsoft-Windows-LanguageFeatures-Basic — проверка правописания для различных языков и раскладок клавиатуры;
• Microsoft-Windows-LanguageFeatures-Fonts — национальные шрифты, например, азиатские
• Microsoft-Windows-LanguageFeatures-OCR — средства для распознавания шрифтов
• Microsoft-Windows-LanguageFeatures-Handwriting — средства для распознавания рукописного ввода
• Microsoft-Windows-LanguageFeatures-TextToSpeech — средства преобразования текста в голос, используемые подсказчиком Cortana
• Microsoft-Windows-LanguageFeatures-Speech — распознавание голоса
• Microsoft-Windows-InternationalFeatures — пакеты национальных настроек, например, для Тайваня

Итак, для добавления таких FOD компонентов, используйте команды вида (замените имя компонента):

Dism /Online /Add-Capability /CapabilityName:Language.Basic

Для удаления FOD:

Dism /Online /Remove-Capability /CapabilityName:Language.Basic

Установка и переустановка пакетов языков (Language Interface Packs, LIP)

Язык интерфейса Windows можно поменять, установив так называемые LIP. ранее они назывались MUI (Multi user interface). Файлы LIP выглядят так: Microsoft-Windows-Client-Language-Pack_x64_es-es.cab для испанского языка. Выглядеть установка будет примерно так:

Dism /Add-Package /online /PackagePath:»C:\Languages\Microsoft-Windows-Client-Language-Pack_x64_fr-fr.cab»

Dism /Remove-Package /online /PackageName:Microsoft-Windows-Client-LanguagePack-Package

В следующей статье мы поговорим как с помощью DISM и Powershell управлять так называемыми Modern-приложениями AppX.

Personal Computer Components and Subsystems

This chapter is from the book

This chapter is from the book

This chapter is from the book 

• Hardware Components
• Software Components
• PC Boot Process

Several core components and ancillary subsystems comprise PCs. The core components provide the basic functionality of the PC. Ancillary subsystems enhance the basic functionality to support different applications, such as graphics imaging, multimedia applications, and more. PCs are a package of matched components. The components are matched for speed (somewhat tuned) to provide the best overall performance. It makes little sense to have a super fast Central Processing Unit (CPU) chip and a slow fixed disk drive or slow Random Access Memory (RAM). Such a combination produces a slow system. PCs are as fast as their most used and slowest component. Sometimes fixing PC problems is making sure that the PC components are properly matched for speed. However, the best PC is always the most reliable PC. Nerds may brag about their fast PCs, but their PCs rarely fail.

The PC core components ranked from fastest to slowest are:

• CPU chip—fastest
• RAM
• Display adapter
• Read-Only Memory (ROM)
• Fixed disk drive
• Universal Serial Bus (USB)
• Network adapter
• CD-ROM drive
• CD Rewriteable (CD-RW) drive
• Digital Versatile Disk (DVD) drive
• Floppy disk drive
• Parallel port
• Serial port
• Mouse
• Keyboard
• The nut behind the keyboard—slowest

Components and subsystems fall into three categories: hardware, software, and network. Hardware components are those components physically installed in the PC or connected to it. They are the core and ancillary subsystems examined in this chapter. Software components are covered in Chapter 9 through Chapter 16. Network connections are common components of most PC systems today.

Network connections are either dialup or Local Area Network (LAN). Cable modem and Digital Subscriber Line (DSL) connections are LAN connections as well. The network connections are attached to PC hardware components and work in conjunction with other computers and networking hardware residing somewhere on the attached network. I discuss networking as it impacts the PC hardware and software components and subsystems, but networks and external networking components are beyond the scope of this book.

Hardware Components

PC hardware is the focus of this section. PC hardware core components include the CPU chip, the ROM, the RAM, chip sets and buses, the power supply, serial and parallel Input/Output (I/O) ports, the floppy disk controller and drive, the fixed disk controller and drive, the CD-ROM drive, the DVD-ROM drive, the display adapter and monitor, the keyboard, and the mouse. See Figure 1–1. These components provide all basic PC functions. Ancillary subsystems are sound cards, LAN adapters, video cameras, and so forth.

Figure 1-1 Typical PC system.

The main PC chassis contains the central component for all PCs, the Main Logic Board (MLB). This is sometimes referred to as the system board or motherboard.

The MLB is based on a specific CPU and supporting chip set. It has a specific bus configuration and mounts the CPU, the ROM, and the RAM. Serial and parallel interfaces, as well as the keyboard interface, bus mouse interface, floppy disk controller, fixed disk Integrated Drive Electronics (IDE) controllers, and USB ports are typically built into the MLB. Proprietary systems and laptop PCs have Video Graphics Array (VGA) display controllers incorporated into the MLB as well. Other controllers are bus-connected cards inserted into the bus of the MLB.

Main Chassis

The main chassis or case is the box containing most PC components. Components may be connected to the main chassis using USB connections. The main chassis would then contain the PC’s core components, and the ancillary subsystems would occupy desktop space.

The main chassis for the PC Advanced Technology (AT) contained the MLB, its installed Intel 286 CPU chip, ROM, and RAM. The supporting chip sets provided Industry Standard Architecture (ISA) 8-bit and 16-bit connectors for installing adapter cards. Adapter cards typically installed in the AT were serial and parallel I/O controllers, display adapters, and disk controllers. The typical AT style PC chassis contained the floppy drive(s) and a fixed disk. The primary user input was by a keyboard. This was the typical 1985 PC.

In the early 1990s, PCs changed. At that time, Microsoft Windows made a successful entrance into the PC marketplace. It pressured PC manufacturers to change main chassis components more rapidly than before. Similar to the 1980s PCs, most MLBs had an installed Intel 386 or 486 CPU chip—although some supported Advanced Micro Devices (AMD) CPU chips—external CPU cache RAM, ROM, and RAM. The MLB also included the serial and parallel port I/O controllers and IDE fixed disk and floppy disk controllers. The bus connections were mainly ISA 8-bit and 16-bit connectors. Some systems had specialized connectors to speed up display and disk access. The Video Electronics Standards Association (VESA) bus and Extended Industry Standard Architecture (EISA) MLBs had connectors that supported higher speed transfers than the ISA bus connectors.

Now PCs incorporate both these evolutionary changes and revolutionary changes. Their MLB typically has Intel Pentium or AMD Athlon chips, RAM, ROM, built-in floppy disk, IDE fixed disk, USB, bus mouse, and keyboard controllers. PCs sometimes include a VGA controller and soundcard components as well. The chip sets and Basic Input/Output System (BIOS) support plug-and-play controller installation and sometimes a combination of ISA and Peripheral Component Interconnect (PCI) bus connectors. New MLBs are moving rapidly toward legacy-free configurations that support only plug-and-play PCI bus and USB components. This just means that it will not be your father’s PC anymore. Also, maintenance and troubleshooting procedures change to accommodate new types of problems posed by these newer PC technologies.

System Board—MLB

The MLB, system board, or motherboard is the physical foundation of a computer. Baseboard, planar board, or main boards are other terms used to identify the MLB. It is the central PC building block because all other components must either plug into it or be physically mounted on it. Without a system board, no electrical interconnectivity is available to allow the PC’s hardware components and subsystems to communicate.

System boards come in different configurations including:

Extended Technology (XT) style

Advanced Technology Extensions (ATX) form factor and Mini ATX form factor

Micro ATX form factor

Flex ATX form factor

NLX form factor

The early boards emulated an IBM PC XT configuration and then the IBM PC AT configuration. As chip sets incorporated greater functionality, MLBs shrank in size and, at the same time, incorporated more functions. The next generation of system boards had a standardized Baby AT form factor. This meant that they had one dimension that was from 8.6 to 8.8 inches and had specially placed mounting holes for plastic standoffs and bolts. Brand name PC manufacturers used proprietary system board configurations. Such proprietary configurations necessitated that replacement MLBs be provided from the PC manufacturer. These proprietary configurations limit the ability to upgrade PCs with faster CPU chips, RAM, and other capabilities. The ability to increase RAM, upgrade CPU chips, and swap adapter cards is designed into these proprietary MLBs, but such upgrade capabilities do not offer as many upgraded components as when an entire MLB is replaced. See Figure 1–2. For more detail on MLBs, see Chapter 5.

Figure 1-2 Baby AT Slot 1 and Socket 7 (with AMD CPU) MLB.

Today’s PCs use MLBs that have ATX, Mini ATX, Micro ATX, Flex ATX, and NLX form factors. ATX form factor MLBs evolved from the Baby AT MLBs. Basically, the Baby AT MLB was rotated 90 degrees from its position facing the rear of a PC chassis, and a new power supply connection configuration was added. The longer ATX style boards permit relocation of the CPU and mounting of memory on the board. The longer ATX board also allows full-length expansion card slots and permits more I/O functions installed as components on the MLB.

ATX form factor MLBs have up to seven expansion slots and external connectors for the PS/2-style keyboard and mouse, as well as serial, parallel, and USB connections installed directly on the MLB. Some ATX form factor MLBs also include a sound card and added USB connections. Figure 1–3 shows a dual Slot 1 ATX MLB with the PS/2-style keyboard and mouse connectors on the lower-left bottom of the figure. USB connectors are next to the keyboard and mouse connectors. Communication (COM) port and parallel port connectors are near the middle of the ATX-style MLB. ATX MLBs are 12 inches by 9.6 inches with specially placed mounting holes for standoffs and bolts. Mini ATX MLBs were the first variation of the ATX MLB form factor. The Mini ATX MLB was 11.2 inches by 8.2 inches.

Figure 1-3 ATX Slot 1 MLB.

Micro ATX MLBs followed the Mini ATX MLB and are smaller still with a 9.6 inch by 9.6 inch maximum size. Similar to the ATX MLB, the micro ATX MLB has built-in connections for mouse, keyboard, USB, serial, and parallel connectors. It supports up to four expansion card slots that may be a combination of ISA, PCI, ISA/PCI, and Accelerated Graphics Port (AGP) bus slots. The MLB-installed components may include standard connections, as well as Musical Instrument Digital Interface (MIDI)/game and audio output connections.

The Flex ATX MLB is also a smaller board. Its dimensions are 9.0 inches by 7.5 inches. It has the same mounting as the Micro ATX MLB and the same standard ATX rear I/O panel. The smaller packaging of the Flex ATX reduces the overall system manufacturing costs, resulting in lower total system cost to the PC user.

NLX MLBs are designed for low-profile PC systems. They support current and future processor technologies, AGP, tall Dual Inline Memory Modules (DIMMs), and flexible installation without screws. An AGP bus connector may be mounted on the MLB, but ISA and PCI bus expansion slots cannot. Thus, a distinguishing NLX motherboard characteristic is that the PCI and ISA bus card slots are implemented in a riser card into which the MLB inserts. The NLX riser card can support up to five PCI bus slots and an unspecified (but low, like one or two) number of ISA bus slots. The expansion cards are inserted parallel to the MLB and not vertically into the MLB. The NLX motherboard may be 8.0 inches or 9.0 inches wide and 10 inches, 11.2 inches, or 13.6 inches long.

One key area of evolution for the MLBs is in the power supply interface. The older boards used a power supply with a built-in power switch. In this case, the high-voltage (120 or 220 Volts Alternating Current [VAC]) wires were only exposed if the power supply case was opened. Other AT-style power supplies had an external front panel switch. This meant that the high-voltage wires ran from the power supply to the front panel switch, exposing them whenever the PC case was open. The ATX power supplies terminate the high-voltage wires in the power supply and control the PC power on/off function through a low-voltage MLB control circuit and internal power relay. The front panel power switch plugs into the ATX MLB using a low-voltage connection. Viewing any of the main boards, you see sockets for the CPU chip (or the Intel Slot 1 and AMD Slot A carriers) and sockets for RAM, PCI, AGP, and sometimes ISA 16-bit bus connectors. Plugs for the power supply cables are also on the main board.

To examine a system board, a PC’s cover must be removed. After you get inside, the system board typically is the largest sheet of green or brown fiberglass mounted directly to the metal frame or chassis. In an older desktop chassis, the system board was typically mounted on the bottom. With the newer tower configuration chassis, the system board is mounted vertically. System boards are multilayer boards with four to seven or more layers of connections sandwiched between the layers of fiberglass. All layouts have keyboard and mouse connectors in the right rear corner of the board. (If you were facing a desktop PC, the connections would be in the rear on the right.) See Figure 1–4.

Figure 1-4 Mini-tower chassis with control, Light-Emitting Diode (LED), and speaker connection detail.

Looking more closely, you will find a number of lines running across the system board in an organized pattern, connecting different areas of the system board together. Physically mounted on the system board should be a few different types of connectors and chips.

The CPU is a computer on a chip. The CPU chip acts as the hands or heart of the computer. There are no brains here because computers are dumb. They only do what they are told. They are the hands that perform the work as directed and the heart that pumps the data to all PC components.

Processors are classified by their interface to the MBL and by processing horsepower. MLB interfaces are a socket interface or a slot interface. The socket interfaces are Socket 7 (Intel Pentium CPUs) and Socket 8 (Intel PentiumPro CPUs). Intel introduced the Single Edge Contact (SEC) or slot interfaces in 1998. Most slot interfaces are Slot 1, but some Intel chips may use the Slot 2 interface, and AMD Athlon chips use a Slot A interface. Newer chips have returned to socket mounting with Intel’s Socket 370, Socket 423, and Socket 478 and AMD’s Socket A (Socket 462) mounting. See Figure 1–5. Processing horsepower is mostly defined by clock speed. CPU purists would argue that point vigorously. However, general users would only notice performance improvements when clock speeds increase by greater than 50 percent.

Figure 1-5 AMD Athlon Thunderbird CPU chip.

Other components in the CPU also determine its performance, including the amount of Level 1 (L1) and Level 2 (L2) CPU cache incorporated into the chip configuration.

Starting with the 486 chips, CPUs had internal Level 1 CPU cache memory to speed up processing performance. Both Level 1 and Level 2 cache are a storage area used by processors to increase performance. Level 1 is a small, high-speed cache right on the chip, which holds recently used data and instructions from memory. Level 2 is larger in size and, until recent years, has been located outside the chip on the motherboard. PentiumPro chips were among the first to include the Level 2 CPU cache in the chip package. The latest Intel and AMD chips have both Level 1 and Level 2 CPU cache memory inside the chip to maximize performance.

Cache memory is a means of speeding up computer processing. Cache works on the 80/20 rule of computers. This is similar to the 80/20 rule of the Internal Revenue Service (IRS). They keep 80 percent of what you earn, and you get 20 percent of what you earn. In computers, 80 percent of the time, the next piece of information that you need is right next to the last piece of information that you used. This means that, if information is contained on a device, like a disk drive, that is slower than the component where the information is going to be used next, like RAM, it makes sense to bring the information into a temporary holding area—the cache—that is faster than the disk drive. In this case, 80 percent of the time the data is retrieved from the cache, and 20 percent of the time the data is received directly from the slower disk drive. This is disk cache operation.

To really envision cache operation, think of baking cookies. You go to the cupboard and get flour, then go back to get sugar, and go again to get chocolate chips, and finally go to get spices. Next, it is on to the refrigerator to get milk, then butter, and, finally, eggs. How much would it speed up cookie baking if you went to the cupboard and got the flour, sugar, chocolate chips, and spices all at once and put them on the countertop, the cookie baking cache? You could then get the milk, butter, and eggs and also place them on the countertop as well.

CPU cache performs similar functions between the faster CPU and the slower RAM. Level 1 cache inside the CPU chip runs at the same speed as the CPU chip, but RAM is from three to 10 times slower than the CPU and the Level 1 cache. Even Level 2 CPU cache external to the CPU chip is half the speed of the CPU. Anything external to the CPU chip requires a relatively long time for the electrical signals to travel from it into the chip; that makes it much slower than anything inside the chip. It is similar to communication by satellite versus terrestrial links. Electrical signals must travel 44,000 miles across some satellite links versus 3,000 miles across a terrestrial link. It means that the signals require approximately 11 times longer completing the trip by satellite.

Most PC chips today are based upon the x86 instruction set developed by Intel. Manufacturers like AMD and VIA Technology’s Cyrix produce chips that emulate the instruction set of the Intel chip. This is possible because of cross-licensing of technology and patents between manufacturers. All of these competing chips run PC software equally well. See Table 1–1.

Table 1–1 CPU Chip Summary

Intel Pentium 4

Uses Intel Pentium III instructions with added multimedia instructions, has a special trace transfer cache, uses Rambus Dynamic RAM (DRAM), and is based upon copper technology

Intel’s latest and greatest is no longer a Slot 1 cartridge. This chip is a Socket 423 or Socket 478 chip.

Intel Pentium III

MMX, Single Instruction-Stream, Multiple Data-Stream (SIMD) instructions, and internal Level 2 cache inside the cartridge

Best performance chip.

Intel Pentium II

MMX and external Level 2 cache inside the cartridge

Cheapest chip. This is a Socket 370 chip.

Intel Celeron 266/300

MMX, but no Level 2 cache

Cheap Intel. This is a slow performer.

Intel Celeron 300a/333/366/400/ 433/466/500/533/566/600/633/667/700/733/766/800

MMX and 128 kilobyte (KB) inside chip Level 2 cache

Cheap Intel. This is a competitive performer.

Initial MMX and external Level 2 cache

This is at the end of life.

No MMX and large internal Level 2 cache

This is a Windows NT server chip that is at the end of life.

Xeon Pentium III

MMX, SIMD instructions, and large internal Level 2 cache

New Windows NT/Windows 2000 server chip.

Explicitly Parallel Instruction Computing (EPIC) architecture and 64-bit CPU. Has Level 1, Level 2, and Level 3 internal cache

Server chip for Windows NT/Windows 2000, Linux, and NetWare.

Initial MMX and external Level 2 cache

Good Pentium MMX competitor.

3D; improved MMX and external Level 2 cache

Good Pentium II competitor.

3D; improved MMX and internal Level 2 cache

Best Pentium II competitor.

3D; improved MMX and inside the cartridge Level 2 cache

Slot A design competitor to Slot 1

Thunderbird chips have internal Level 2 cache

Newer Thunderbird chips return to socket technology and use Socket A or Socket 462.

MMX and external Level 2 cache

Good for business applications, but poor for imaging and Computer-Aided Design (CAD). Less widely sold than AMD and Intel CPU chips.

3D; improved MMX and internal 128 KB Level 1 cache

The VIA Cyrix® III processor is designed for cheap PCs and notebooks, as well as the new generation of information appliances.

ROM contains the start-up code and the 16-bit BIOS programs for the PC. ROM is divided into system ROM installed on the MLB and adapter ROM installed on adapter cards. See Figure 1–6.

Figure 1-6 Keyboard and main BIOS ROM chips on MLB.

System ROM is first accessed during the boot process. It performs the initial PC setup, loads the PC’s cold boot loader program from the fixed disk Master Boot Record (MBR), and handles the PC’s I/O operations under the Disk Operating System (DOS). Most PCs have 64 KB of ROM. The addresses are mapped into the last 64 KB memory page below the memory boundary. Some PCs have more system ROM. The most notable was the Micro Channel Architecture (MCA) IBM PS/2. To operate the MCA bus and its jumperless hardware installation, 128 KB of ROM was used. The MCA bus PC was the predecessor to the PCI bus plug-and-play designs that we have today. Plug-and-play PCs use special ROM code to implement plug-and-play. This ROM code does not, however, increase the system ROM size beyond 64 KB. Other PC cards also contain ROM. Adapter ROMs perform special adapter card operations. They handle I/O operation, or, in the case of some Small Computer System Interface (SCSI) adapters, they perform setup and diagnostic operations. Adaptec has ROM on its SCSI adapters; SCSI Select software configures the adapter, functions as a diagnostic program, and formats the SCSI drives attached. Virtually all display adapters have some type of video ROM. This ROM is about 32 KB in size. It is placed in the PC address range 832 KB to 864 KB (C000-C7FF). More details on memory addressing and ROM locations are provided in Chapter 9.

RAM is the working area of the PC. All data must flow into and out of RAM. It holds both programs and data. When a program is running (executing) and working on data, the program and most often the data reside in RAM. In a Windows environment, RAM is virtualized. The operating system has 4 gigabytes (GB) of virtual memory where components and applications can reside. Windows translates the virtual address space into a combination of disk accesses and memory paging and allocation, translating the virtual address space into real physical PC RAM and disk addresses. When any PC is running, most of its electronic activity involves swapping data between RAM and the CPU. When the PC is powered down, the data in RAM is lost. The PC’s maximum RAM capacity has moved from 1 megabyte (MB) to 16 MB and up to 4 GB or more today for many servers. Most PC RAM is comprised of DRAM chips that must be continually refreshed. Thousands of capacitors acting like leaky buckets comprise DRAM. Static RAM (SRAM) acts like small switches that, after they are set, do not need to be refreshed. SRAM is very fast and more expensive than DRAM. SRAM is used for external CPU cache.

Older forms of RAM employed a parity chip for error checking. The parity chip created an extra bit depending upon just how many ones are in the byte or character stored. When the character is read from memory, the parity is recomputed and compared to the originally stored value. If they matched, everything was OK. If they did not match, older PCs signaled «201» or «Parity Check 2.»

Newer memory chips are placed on modules that are minicircuit boards called Single Inline Memory Modules (SIMMs), DIMMs, or Rambus Inline Memory Modules (RIMMs). SIMMs, DIMMs, and RIMMs provide an entire bank of memory on the minicircuit board. Replacement involves replacing the entire minicircuit board instead of a single bad chip.

RAM is rated and classified by access time. The slowest RAM chips were 250 nanoseconds (ns), and the fastest is around 10 ns. Typically RAM chip speeds are about 50 to 70 ns. For more details on RAM, see Chapter 5.

Other types of RAM are Synchronous DRAM (SDRAM) and Extended Data Output (EDO) RAM. These are both DRAM that needs refreshing. They are, however, more tuned to the CPU chip’s clocking and memory refresh operations and therefore speed up the PC by reducing CPU to memory transfer times.

Newer RAM types are Double Data Rate RAM (DDR RAM) and Rambus DRAM. DDR RAM moves data on every bus clock signal change, not just on leading edge changes. SDRAM operates at 100 megahertz (MHz), and the equivalent DDR RAM would then operate at 200 MHz. Rambus DRAM is a new RAM technology that increases RAM speed to 400 MHz or higher. The higher RAM operating speed does not necessarily mean that Rambus DRAM PCs are faster than DDR RAM PCs because the delay increases when accessing different parts of Rambus DRAM.

Nonvolatile RAM (NVRAM)

There is also NVRAM. This is similar to ROM in that it does not lose its contents when the PC is powered off. NVRAM is SRAM that retains its databits as long as power is supplied to the memory. NVRAM contents are saved when a computer is powered off or its external power is lost, and it is implemented using SRAM with battery power or by using an electrically Erasable Programmable ROM (EPROM).

Like RAM, NVRAM can also be written into. However, writing into NVRAM requires special software. Hence, NVRAM is used to hold ROM BIOS code that may need to be updated or changed. Flashing programs with names such as PHLASH and AWDFLASH update this information. Some modems store preset or user-specified phone numbers and modem profiles using NVRAM. They are specially designed to write the information into NVRAM without using a separate flashing program.

The BIOS is implemented in ROM or NVRAM. It is the code in the PC that boots the PC and controls I/O operations under DOS. Windows uses 32-bit driver software to perform the functions of ROM BIOS routines. The original PC BIOS had a built-in Basic interpreter program for the Basic programming language. Around 1990, that Basic interpreter code disappeared from even the IBM PC’s BIOS. BIOS could be considered as only that part of ROM controlling I/O functions in the PC. However, a broader view would define BIOS functions as:

Hardware setup—During boot, the PC allows you to enter hardware setup options and configure the PC’s standard and advanced hardware options.

Power-On Self-Test (POST) diagnostics—Performs cursory hardware testing to ensure that the PC hardware matches the setup parameters. These diagnostics are only effective in detecting major PC component malfunctions.

Cold boot loading functions—Loads DOS from a diskette or loads the cold boot loader program from the fixed disk’s MBR. It also loads the initial disk drive parameters from the fixed disk partition table.

DOS I/O operations—Provides basic floppy disk, keyboard, display, and fixed disk I/O control operations.

With Windows, these BIOS functions are used during the initial system startup and then replaced by Windows 32-bit driver software.

Firmware

Firmware is PC component driver programs installed in ROM or NVRAM. Firmware was initially used to store hardware setup and BIOS routines because it was easier to update than hardware. In contrast, software stored on disk is the most flexible and easy to change. Firmware typically controls a PC when it is first switched on. Typical firmware would perform cold boot loading of the operating system from a fixed disk or from a network and then pass control to the operating system.

Complementary Metal Oxide Semiconductors (CMOS)

CMOS really describes a chip technology that uses low power. This technology was originally employed in the PC AT to store hardware configuration information in a nonvolatile battery-powered memory chip. A three- or six-volt lithium battery powered the CMOS memory chip. Today, CMOS technology is used in chips in almost all PCs to reduce power consumption. «CMOS» as a term is used to identify the PC’s nonvolatile parameter storage memory, initially implemented with CMOS technology. See Figure 1–7.

Figure 1-7 CMOS batteries.

When the PC is booted, the setup software implemented in ROM changes the PC operating parameters in CMOS memory. These parameters and the CMOS memory addresses are mapped into the first 64 KB memory bank. CMOS is much smaller than 64 KB. Most ROM BIOS setup programs automatically detect disk drive types and CPU speeds and set the PC up to run. CMOS setup parameters are not required for basic PC operation, but rather to tweak the PC for optimal performance. Be careful when changing any CMOS settings because, most often, what seems to be the best or fastest setting can cause the PC to go slower or to malfunction. Default CMOS operating parameters and automatically detected parameters are always the best bet when setting up a PC.

Onboard Controllers

MLBs have built-in controllers for the keyboard, a bus mouse, serial ports, parallel ports, floppy disk drives, IDE fixed disk drives, CD-ROMs, and USB ports. Some servers have onboard SCSI controllers as well.

The first onboard controllers were for the keyboard and the serial and parallel ports. Next, systems incorporated bus mouse ports and floppy and fixed disk drive controllers. These ports were initially routed to outside the PC chassis by pigtail connectors that fit into the expansion slot card covers at the rear of the PC. Such pigtail connections were used on Baby AT system boards. Disk drive controllers had parallel cables attached directly to the stake pin connectors on the MLB. Today, these onboard controllers have their ports directly routed to a special connector area at the right rear of the MLB. This is an ATX MLB configuration.

MLBs typically had two Enhanced Integrated Drive Electronics (EIDE) controllers as shown in Figure 1–8. EIDE onboard controllers have increased transfer speed from 33 MHz Direct Memory Access (DMA) clock speed to 66 MHz DMA and 100 MHz DMA speeds. The number of MLB integral EIDE controllers has also doubled from two to four controllers on some MLBs. This permits those MLBs to support up to eight EIDE devices. The best performance is realized by assigning a single EIDE device to each controller. For example, two fixed disk drives, a DVD drive, and a CD-RW drive could be each connected to a separate EIDE controller to maximize performance because EIDE commands could be executed concurrently, which speeds up copying data from drive to drive.

Figure 1-8 MLB primary and secondary IDE bus connectors.

Expansion Slots

Expansion slots implement the PC’s system bus. The system bus connectors allow other circuit cards to be plugged into them. Because they are card edge connectors, they are called expansion slots. The cards inserted in the edge-style bus connectors are referred to as daughter cards or expansion cards. The daughter card label was used because the cards were inserted into the motherboard.

The expansion slots had different configurations depending upon the bus supported by the system board. The simplest configuration was the 8-bit ISA bus used in the original PC. These bus expansion slots evolved to a 16-bit ISA bus and then on to a 32-bit EISA configuration. The physical size of the EISA slots was the same as the 16-bit ISA slots except the EISA slots permitted the expansion cards to plug deeper into the connector. Thus, EISA slots could support 8-bit, 16-bit, and 32-bit I/O transfers. Table 1–2 identifies expansion slots found in different PC systems.

Table 1–2 Expansion Slot versus PC System

Expansion Slot or Bus

ISA 16 bit + VESA Local (VL)-Bus

386, 486, and Pentium

386, 486, and Pentium

ISA 16 bit + PCI

Pentium Class PCs built in 2000 and before 2000

Pentium Class PCs built after 2000

Personal Computer Memory Card Industry Association (PCMCIA) or Card Bus

Pentium class PCs built after the late 1990s

In early PCs, expansion slots were used for virtually all upgrades to the PC’s basic capabilities, including RAM expansion. I had a PC AT that had 12 MB of RAM installed on several RAM expansion cards. The maximum RAM supported by the PC AT 80286 chip was 16 MB. This is not possible with today’s PCs because RAM transfer to the CPU chip is at much higher speeds than the expansion slots and their buses can run. The top bus clock speed has increased from 8 MHz, to 33 MHz, to 66 MHz, and to 100 MHz. Front side bus (the CPU to RAM bus) speeds have increased from 66 MHz, to 100 MHz, to 133 MHz, to 200MHz, to 266 MHz, and to 400 MHz. This is slow when compared to the 1.5 gigahertz (GHz) and higher clock speeds of CPU chips.

Expansion slots are used to install disk controllers, display controllers, modems, video capture, and LAN adapter cards in the PC. Each type of adapter card enhances the functionality of the basic PC system. These adapters typically run at speeds that match the bus clock speed.

Typical PC expansion slots include ISA 16-bit, PCI, and AGP slots. See Figure 1–9.

Figure 1-9 PC MLB ISA 16-bit, PCI, and AGP expansion slots.

Power Supply

The PC power supply converts 120/240 volt Alternating Current (AC) into the 5- and 12-volt Direct Current (DC) used by the PC. Power supplies are rated by wattage. They range from 85 watts for the original PC to 300 watts for high-end PC power supplies. A watt is a power measurement that is voltage times the amperage delivered by the supply. Because voltage is the same for all supplies, a higher wattage translates into more current being delivered by the supply.

The original PC chips operated using Transistor-to-Transistor Logic (TTL) re-quiring 5-volt DC. The CPU chips of today’s PCs can use lower voltage levels. Typically, these chips employ special voltage regulation incorporated into the MLB.

The original PC power supplies had built-in power on/off switches and power connectors for the MLB and the disk drives. As the PC changed, the power supplies did, too. Current power supplies are typically 230 to 250 watts. They have power connectors for either an AT-style or an ATX-style MLB. Additional power connectors support fixed disk drives, 3.5-inch floppy drives, and front panel lights. Each such connector has a different physical configuration. Furthermore, the power on/off switch is no longer on the side of the supply, but rather mounted on the front of the PC. See Figure 1–10. This necessitates an insulated power connection to a front panel PC power switch. As discussed earlier in the System Board—MLB section of this chapter, newer ATX-style MLBs control the power on/off function by a low-power connection to the MLB. For further discussion on the types of connectors, see Chapter 5.

Figure 1-10 AT-style power supply with front panel switch.

Fixed Disk Drives and Controllers

The fixed disk drive is the file cabinet of the PC. It is the device that holds all software and data while the PC is running and after the PC is powered down.

Fixed disks are described by their capacity, speed, physical size (form factor), and controller interface. Fixed disk capacities range from 8 GB to more than 80 GB. The largest IDE drives are over 80 GB in capacity. Fixed disk drives have Power-On Hour (POH) Mean Time Between Failure (MTBF) rates ranging from 150,000 POH to 1,000,000 POH.

Fixed disk speed is measured by the time it takes for the disk drive read-write heads to seek the data on the disk and the time it takes to transfer data from the disk to the PC’s disk controller. Head seek times are influenced by the physical size of the drive, with smaller drives having better seek times because the read-write heads have shorter distances to travel. Typical seek times range from 8 milliseconds to just over 10 milliseconds. Fixed disk transfer rate is largely determined by the rotational speed of the disk. Disk drives originally rotated at 3,600 Revolutions Per Minute (RPM).

Today’s disk drives range in rotational speed from 4,500 RPM to 15,000 RPM. The higher the rotational speed means the higher the disk drive transfer rate.

The physical size of the disk drives ranges from 1 to 2.5-inch quarter-height drives, to 3.5-inch third or half-height drives, and on to 5.25-inch full-height drives. Other form factor combinations exist as well. The form factor describes the size of the disk—1 inch, 2.5 inches, 3.5 inches, and 5.25 inches—and the height of the drive, with a full-height drive being 3.25 inches high.

Fixed disk drive interfaces are most often IDE, EIDE, or SCSI.

IDE and EIDE

Disk drive interfaces started with the Modified Frequency Modulation (MFM) interfaces that were standardized by the Seagate ST-402 and ST-512 specifications. These interfaces required two cables to the disk drive from the disk controller card. One cable (the wide one) handled 8 bits of data and the drive control signals, and the other (the narrow one) handled the second 8 bits of data. The data and control cable were an extension of the floppy disk interface. It was a 34-conductor cable. The second data-only cable was a 16-conductor cable.

IDE interface disk drives having the drive controller built on the drive displaced MFM drives within a few years. This integration of controller and drive greatly simplified the control interface in the PC. The IDE interface is used today for both fixed disks and CD-ROM drives. It employs a single 40-conductor cable. See Figure 1–11. EIDE controllers provide improved transfer speeds and the ability to interface to four drives.

Figure 1-11 IDE drive cable connection.

Today, IDE and EIDE interfaces can burst transfer data at 33, 66, or 100 MB per second. The largest IDE drives are around 80 GB, with their size expected to increase in the next few years. IDE and EIDE drives are the most commonly installed drives in PCs.

Apple pioneered the SCSI. It was used to connect peripherals to Apple computers. This was the SCSI-I interface that transferred data at 5 MB per second. SCSI became the interface of preference for large-capacity drives. SCSI was relatively expensive because not only were the drives expensive, but they required the addition of a SCSI interface card.

The great advantage of the SCSI besides the increased drive capacity was the ability to connect up to seven drives on the same SCSI interface. This made it possible to build much larger disk volumes and to implement Redundant Array of Independent Disk (RAID) drives. The first CD-ROMs employed SCSI interfaces, but they have since migrated to the EIDE interface.

Many SCSI drives use a single 50-conductor parallel cable with terminating resistors at each end of the bus, which is often the end of the cable. This cable has changed as the SCSI interface speed increased. SCSI started with the Apple SCSI-I speed of 5 MB per second. Early PC SCSI drives operated at this speed. Because the SCSI bus was shared, the transfer speed increased rapidly to provide adequate PC performance. The SCSI bus was changed to fast operation, increasing the transfer speed to 10 MB per second. The fast SCSI set the basic clock rate for the SCSI interface at 10 MHz. The SCSI-II PC controllers operated at this speed. They transferred one byte at a time at 10 MHz, thus producing the 10 MB per second transfer rate.

The SCSI interface was upgraded to the fast wide SCSI that transferred 16 bits, increasing SCSI bus speed to 20 MB per second. The next enhancement was to improve the fast operating speed to 20 MHz with the 16-bit ultrawide SCSI bus, thus providing 40 MB per second transfers. Finally, we have Ultra-2 SCSI capable of 80 MB per second transfers, accomplished using a 40 MHz bus or a 32-bit bus operating at 20 MHz. The SCSI cables changed from the original 50-conductor cable to a 68-conductor cable and finally to fiber optic SCSI channels.

SCSI drives and interfaces are prevalent and preferred in high-end PC and network servers requiring RAID and high-capacity drives. Because the SCSI bus is shared, the transfer speeds of the fastest SCSI buses are divided among the drives attached to the controller. Depending upon the PC use, such a division might enhance overall PC performance. Such enhanced performance, while measurable, is not likely noticeable by most users.

Table 1–3 provides a summary of these interfaces, their characteristics, and their differences.

Table 1–3 Interface Types and Characteristics

Distance of Cable Single Ended

Number of devices

Ultra-2 Wide SCSI

12 meters, but must be LVD cabling

Three types of cabling are most used with SCSI: single ended, differential, or Low Voltage Differential (LVD). Single ended has been the most commonly used through the years because of its low cost in comparison to differential. Now, with the higher speeds, single ended is very limited in the distance of cabling. Differential cabling is more expensive then single ended, but can do all speeds up to 25 meters, so it is used in long runs of external cabling. LVD is relatively new on the market and is supposed to have the best of both worlds because it can run all speeds of SCSI up to 12.5 meters at a much lower cost than differential. Remember, do not mix your SCSI cabling types; they are electrically incompatible.

Microdrives

New, very small fixed disk drives are being used in a variety of electronic equipment. Pioneered by IBM, microdrives provide 340 MB to 1 GB storage capacity for portable electronic devices in an industry-standard Compact Flash + (CF+) Type II form factor and an AT Attachment (ATA)/PCMCIA Type II interface support with appropriate adapter. The high-capacity microdrives enable digital cameras to capture more high-resolution photos, enable handheld PCs to access more applications and to maintain large databases, and permit notebook users to back up and to transport their data more quickly and conveniently. A single hard disk microdrive can provide 340 MB, 512 MB, or 1 GB storage capacity in about a 1.5-inch square 16-gram package. Microdrives support a maximum sustained data rate exceeding 4 MB per second.

JAZ and ORB

Iomega developed JAZ drive technology. JAZ drives are floppy disks that rotate at high speeds (5,394 RPM vs. 300 RPM for floppy disk drives). They employ the Bernoulli principle (fast moving air has less pressure than static air, which is what causes planes to fly) to permit the read-write heads to get very close to the floppy disk medium. As a result, they can store substantial amounts of data on 3.5-inch floppy disk cartridges. Because their rotational speed is high compared to floppy drives, they have performance that resembles fixed disks. The newer JAZ drives are capable of storing 2 GB of data on a single removable floppy disk cartridge. JAZ drives interface to the PC using SCSI. See Figure 1–12. JAZ drives can be installed internally or attached externally to the PC. External drives can be moved from PC to PC, using a USB or a FireWire (Institute of Electrical and Electronic Engineers [IEEE] 1394) interface to connect to the PCs. The older JAZ drives interfaced to the PC using the PC’s parallel port, and the PC’s parallel interface was transformed into a SCSI interface using a special Trantor interface cable. JAZ drives have a MTBF of 250,000 POH.

Figure 1–12 JAZ® drive, cartridge, and SCSI interface connectors.

JAZ drives provide removable media storage for PC backups. The benefit of such backup is that the JAZ drive’s operation is similar to random access disks and not like linear access tape backups. Random access can make data accessibility faster than with tape. The limitation here is that each cartridge stores only a maximum of 2 GB of data. JAZ cartridges can be compressed, but this presents problems for the 2-GB capacity cartridges. Because JAZ drives look like older DOS fixed disks to the PC, they are limited to storing only a maximum of 2 GB of data effectively. Thus, when a 2-GB cartridge is compressed, it produces a 2-GB drive and 1-GB hidden drive. The 1-GB drive is usable, but not conveniently so. It is much more effective to compress a 1-GB JAZ cartridge to provide about 2 GB of storage. The 2-GB JAZ drive works with the 1-GB JAZ cartridges.

The ORB drives from Castlewood also store 2.2 GB of data. They perform similarly to the JAZ drives. ORB drives connect to PCs using EIDE and SCSI interfaces for internal drives and SCSI, USB, and FireWire for external drives.

Optical Rewriteable Drives and DVD-RAM Drives

Optical storage drives are similar to JAZ drives. They have an equivalent 2-GB capacity or greater, and they rotate at higher speeds than floppy drives, from 2,400 RPM to 3,755 RPM. (Sony’s external optical drive runs at 3,600 RPM.) Rewriteable optical drives use a SCSI interface like the JAZ drives.

Optical rewriteable drives store data using a magneto-optical storage process. Magnetism is used to permit laser recording of data on the disk media. After it is recorded, the data is read using a laser. The main benefit here is that the recording medium is durable and lasts a long time. Where data in time can be corrupted on JAZ floppy media, it is good for 30 years on rewriteable optical media. The rewriteable optical cartridges use 5.25-inch media that may hold 650 MB, 1 GB, 1.3 GB, 2.6 GB, or 5.2 GB. This is physically larger than the JAZ 3.5-inch media.

The rewriteable optical technology has migrated from the original rewriteable optical drives to rewriteable CD drives (compact disc-erasable [CD-E]) and rewriteable DVD drives. The rewriteable CD drive provides more flexibility and storage capacity at a reduced cost than the original rewriteable optical drives, using a 5.25-inch media similar to a CD. It has the CD recording capacity of 600 to 700 MB. The media does not require a special carrier (container for the media), which the optical rewriteable drive does. Performance is similar to a slower CD-ROM.

Rewriteable DVD drives (also called DVD RAM drives) provide greater storage capacity than other rewriteable drives. Similar to a normal DVD drive, they use a blue laser to enhance storage capacity of the 5.25-inch media. The discs can store 2.6 GB on single-sided discs and 5.2 GB on double-sided discs. They can read and write DVD media and read CD-ROM media. Disc formats supported are DVD-RAM, DVD-R, DVD-ROM, CD-ROM, CD-RW, CD-Extra, and CD-Audio (CD-A). The interface to the PC is typically SCSI for these devices. DVD-RAM drives use rewriteable cartridges that are most commonly sold in a 5.2 GB, double-sided capacity. Some DVD RAM drives have a MTBF of 100,000 POH.

Floppy Disk Drives

Floppy disk drives were the original PC storage media. From 1981 through 1983, there were no PC fixed disk drives. The first fixed disk drive that we saw for a PC was a 5-MB drive that cost $5,000. Months later, IBM marketed the PC XT with its 10-MB fixed disk for $1,000. In the 1981 to 1983 timeframe, we first used single-sided and then double-sided floppy drives as the only permanent data storage for the PC. Of course, everything was smaller then. A large file was 30 KB because it contained ASCII text-only information.

5.25-Inch Floppy Drives

The original PC disk drives stored 160 KB of data on a single-sided 5.25-inch disk. They used 40 tracks with eight sectors per track with each sector storing 512 characters (bytes) of data. The total capacity then was (40 tracks) x (8 sectors) x (.5 KB), equaling 160 KB total capacity. At one time, we were so desperate for storage space that we attached four double-sided floppy disks to a PC. It was the ultimate machine at the time because of its active 1.44-MB storage capacity. See Figure 1–13.

Figure 1–13 5.25-inch floppy disk drive.

These disks were soon replaced by double-sided drives, then nine sector-per-track drives, and, finally, by high-density 5.25-inch drives. Each disk drive enhancement increased the storage capacity. The high-density drives appeared with the PC AT. They stored data on 80 tracks with 15 sectors per track on two sides of the floppy. As always, the sectors contained 512 characters of data. Their capacity was (80 tracks) x (15 sectors per track) x (two sides) x (.5 KB), equaling 1.2 MB per disk.

The disks came in a plastic holder that provided the necessary mechanical support for inserting them into and removing them from the floppy disk drive. A paper sleeve protected the floppy media by covering the read-write window of the diskette.

3.5-Inch Floppy Drives

The 3.5-inch floppy drives came out with the first IBM PS/2 PCs in 1987. They were about two-thirds the width and one-half the height of a 5.25-inch drive. They had new power connections requiring special power supply pigtail adapters to provide power to the drives. Today, all power supplies provide specific 3.5-inch disk drive power connections. The 5.25-inch drives used both 5-volt and 12-volt DC power, while the 3.5-inch drives used 5-volt DC power alone. See Figure 1–14. Some 3.5-inch drives were even smaller in height, and combination 3.5-inch and 5.25-inch drives were developed that fit into a single 5.25-inch half-height drive bay.

Figure 1–14 3.5-inch floppy drive.

The 3.5-inch disk media is mounted in a permanent plastic sleeve with a special sliding door protecting the disk drive media. The sliding door is one of the greater hazards for 3.5-inch drives. The doors are typically made out of aluminum or plastic that is easily bent or broken. Any bending makes the aluminum door catch on the inside of the 3.5-inch drive, causing destruction of the disk and sometimes damage to the drive itself.

The 3.5-inch disk stores data on 80 tracks with 18 sectors per track. This gives a total capacity calculated by multiplying (80 tracks) x (18 sectors per track) x (two sides) x (.5 KB), equaling 1.44 MB per disk. These disks have become, in the late 1990s, the basic DOS boot and initial software installation mechanism for PCs. Their capacity today remains adequate for hardware diagnostics, but it has become insufficient for installing any software. Software installation is largely from CD-ROMs. Newer PCs can boot directly from the CD-ROM to facilitate direct software installation. Some of the latest floppy disk drives rotate at about twice the speed of older floppy drives. This significantly enhances their performance. Their capacity has not been increased, only their data transfer and seek time performance. Newer super disk drives, resembling floppy drives, do enhance both disk capacity and performance.

The typical mean time between failures for a floppy disk drive is 30,000 POH.

Super Disk or Laser Servo (LS) 120 Drives and High Floppy Disk (HiFD) Drives

The Imation, Inc. Super Disk or LS-120 drives stored 120 MB of data on special floppy disks, and Sony’s HiFD can store 200 MB on its special floppy disk. These drives accomplish this by increasing the track density and the sectors-per-track storage density on the floppy media. A more precise LS head positioning mechanism makes this possible. The Super Disk 3.5-inch disks store data on 1,736 tracks with 69 sectors per track. This gives a total capacity calculated by multiplying (1,736 tracks) x (69 sectors per track) x (two sides) x (.5 KB), equaling 119.784 MB per disk.

Super disk drives interface to the PC using either the IDE/ATA Packet Interface (ATAPI), similar to CD-ROMs, or the parallel port, similar to Zip drives. Their performance is similar to parallel interface Zip drives. Super disk drives rotate at 720 RPM, about twice the speed of the older floppy disk drives. The higher rotational speed improves disk drive performance, making super disk drives faster than floppy drives, but somewhat slower than Zip or JAZ drives. Sony’s HiFD drives connect to the PC using a parallel or USB interface.

In spite of their increased capacity, super drives still lack the storage space to act as an effective installation medium for most Windows application programs. Newer applications occupy several hundred MB of disk storage space, thus requiring the storage space on CD-ROMs or on DVD-ROMs to contain the software and supporting data being installed.

Because of the increasing need for storage capacity, Imation stopped selling super disk drives in 2000. Our guess is that these high-capacity, fast floppy disk drives that are backward compatible with 3.5-inch floppies are most likely to be relegated to a niche market in the long run.

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Zip Drives

Zip drives, similar to super disk drives, originally stored 100 MB of data. Newer Zip drives store 250 MB in a 3.5-inch disk cartridge. There are Zip 250 drives that store either 100 MB or 250 MB of data. Zip drives interface to the PC using either a parallel port or SCSI connection. A new USB 100 MB Zip drive is also offered. The Zip 250 drive operates using the original Zip SCSI or parallel port connection. The Zip drives, just like JAZ drives, work based upon the Bernoulli principle, permitting the read-write heads to move close to the floppy recording media and thus providing the ability to store more information and to provide high performance without damage to the media. Zip drives rotate at 2,945 RPM. Their performance is better than the super disk drives due largely to their rotational speed.

The PocketZip™ drives use smaller 2-inch by 2-inch disk cartridges that store 40 MB of data. Similar to microdrives, the PocketZip drives connect to PCs using USB interface.

CD-ROM

CD-ROMs have become a standard part of every PC. They are about to be displaced by the newer higher capacity DVD drives because of the growing need for more information storage capacity on PCs. Such increased information storage capacity will be used to store video (movies) and large databases. For example, the American Automobile Association (AAA) Map ‘n Go software that stores road maps of the United States and Canada on a single CD-ROM is limited by the CD-ROM’s capacity. Therefore, detailed street maps are only provided for specific areas surrounding major cities. The DVD version can have detailed street maps for virtually the entire United States.

Typical CD-ROMs store about 650 MB of data (or 74 minutes of audio recording in CD-A format) on a read-only 5.25-inch plastic media. CD-ROM drives read discs with CD-ROM, CD-RW, CD-Extra (a format supporting a mix of CD-A and CD-ROM information), Motion Picture Experts Group (MPEG) Audio Layer 3 (MP3), and CD-A.

CD-ROMs have become the primary distribution mechanism for virtually all PC software. With the advent of high-speed Internet connectivity, the software distribution and update methodology will change to an Internet focus because of the convenience. This will extend NVRAM upgrading for different hardware devices. For example, we recently upgraded a 3Com-USRobotics modem to the current firmware release by connecting to the 3Com site through the Internet and then dialup communications.

The 1X speed, 2X speed, and higher speed CD-ROM drives are measured relative to the original rotational speed of audio CDs. The 1X CD drives rotated from 210 RPM to 539 RPM, providing Constant Linear Velocity (CLV) as the CD was read from the outside to the inside tracks on the CD. Audio CD specifications are the basis for all CD standards. Higher X speeds mean faster writing speeds. When reading, access and seek times are often better for higher X speeds. Fixed disk drives behave differently. They rotate at one constant speed, producing variable data rates (Constant Angular Velocity [CAV]) as the data is read from the outside to the inside tracks on the disk.

CD-ROMs interface to the PC using the IDE/ATAPI interface. They occupy a single 5.25-inch half-height drive bay. CD-ROMs perform at different speeds and with different data-buffering capabilities. The top speed CD-ROM drives are 72X drives as compared to the original 1X and 2X speed drives. Some drives advertise higher speeds. They accomplish the higher speeds through buffering of data read from the CD-ROM drives. CD-ROMs rotate at variable speeds depending upon the track being read. The rotational speed varies from about 539 RPM to 210 RPM for a 1X drive, with the inside tracks being read at the higher rotational speed. This technique maintains a CLV of the data as it travels under the CD-ROM read heads because inside tracks have less data than outside tracks.

Different types of CD-ROMs have different CD storage formats. CD-ROM formats differ for CDs storing audio only, data, CD-R (Compact Disc-Recorders) data, and CD-RW data. There are also variations for storing photos (Kodak Photo CDs) and video.

CD-R (CD-RW/CD-R) Drives

CD-R drives write and read CD-ROMs. The original CD-R drives have been replaced by the CD-RW drives that can function as a CD-R drive, writing once on CD-R media, and, with the proper CD-RW media, they can write and rewrite recordable CDs. CD-RW drives read prerecorded CD-ROMs, both audio and data, and write and then read recordable CDs. The reading process is at a higher speed than the writing process. CD-RW drives operate at different speeds for reading CDs (up to 40X), writing CD-ROMs (up to 16X), and writing CD-RW media (up to 10X). The first CD-R drives interfaced to the PC using a SCSI bus connection. Most CD-RW drives use the IDE/ATAPI interface standard used by CD-ROM drives. Special software is required to perform the CD writing operation. This software writes data and audio CDs. CD-RW drives require a single half-height 5.25-inch drive bay for mounting in a PC. See Figure 1–15.

Figure 1–15 CD-R drive.

The major benefit of having CD-RW drives is that they can act as a backup for valuable data. In spite of their storage capacity being somewhat limited (650 MB), they are cheap (about $1 per disc) and very transportable. If properly cared for, the life expectancy can be as long as rewriteable optical drives.

There are different types of CD-R discs. Not every type of disc works with every CD-RW drive at the highest recording speed. To ensure that a disc works with a specific drive, you should perform a test of that manufacturer’s media. Often, reducing the recording speed helps in recording the data. CD-RW drives have a MTBF of 30,000 to 60,000 POH.

DVD discs are similar in capabilities to CD-ROMs, but they are capable of storing significantly larger amounts of data. This is possible because they use a different color laser and because they can store data on both sides of the disc. This makes it possible to store 5.2 GB, 8.5 GB, 9.4 GB, or 17 GB of data on a single DVD disc. The single-sided DVD discs store 4.7 GB or 9.4 GB. When reading DVD discs, the drives run at slower speeds than when reading normal CD-ROMs. The DVD reading speeds are up to 16X, while CD-ROM speeds are as high as 72X.

DVD drives support a full variety of DVD and CD formats, including DVD-ROM (DVD-4.7, 8.5, 9.4, and 18), DVD-ROM book, DVD-Video book, CD-Digital Audio (CD-DA), CD-Graphics (CD-G), CD Text, CD-ROM, CD-ROM-Extended Architecture (CD-ROM-XA), CD-Interactive (CD-I), Photo CD, Video CD, CD-R, and CD-RW. This provides backward compatibility with older CD-ROMs and forward compatibility with the enhanced storage capabilities of the newer DVD CDs. Combination DVD and floppy drives are used in laptops. This dual DVD/floppy drive occupies a single laptop PC drive bay. Similar to CD-ROM drives, DVD drives have a MTBF of 100,000 POH.

Disk Drive Summary

Disk drive capabilities are summarized in Table 1–4.

Table 1–4 PC Disk Drives

Approximate Rotational Speed

Physical Drive Size

160 KB to 1.2 MB

5.25-inch half-height drive; 5.25-inch quarter-height drive (combination units)

720 KB to 1.44 MB

3.5-inch half-height drive; 3.5-inch third-height drive; 3.5-inch quarter-height drive (combination units)

LS-120 Super Disk

3.5-inch disk; 3.5-inch Super Disk

300 RPM and 720 RPM

1.44 MB and 120 MB

3.5-inch half-height drive

CF+ Type II that fits a PCMCIA Type II slot with an adapter

5 mm 43 mm 37 mm

1-inch to 5.25-inch

3,600 RPM to 15,000 RPM

5.25-inch full-height to 1-inch quarter-height

210 to 539 RPM for 1X and 3,360 to 8,624 RPM for 16X

5.25-inch half-height drive

210 to 539 RPM for 1X and 3,360 to 8,624 RPM for 16X

5.25-inch half-height drive

2,400 to 3,755 RPM

2.3 GB per side or 4.6 GB total

5.25-inch half-height drive

210 to 539 RPM for 1X and 1,100 to 9,200 RPM for 16X

2.6 GB one side 5.2 GB two sides or 4.7 GB one side 9.4 GB two sides

5.25-inch half-height drive

210 to 539 RPM for 1X write and 420 to 1,078 RPM for 2X read

3.95 GB and 4.7 GB

5.25-inch half-height drive

5.25-inch half-height drive

100 MB to 250 MB

3.5-inch half-height drive

1,200 to 9,200 RPM as a DVD 9,500 RPM CD-ROM

4.7 GB (single layer, single side), 8.5 GB (dual layer, single side), 9.4 GB (single layer, double side) and 17 GB (double layer, double side)

5.25-inch half-height drive

Tape Drives

PCs sometimes come with tape drives for making backups of data on the fixed disk drives. Tape drives store data sequentially on Digital Audio Tape (DAT) tape cartridges. The DAT standard, created in 1987, is a digital recording format providing three hours of digital sound on a tape half the size of an analog cassette tape. The recording format uses a 44.1 kilohertz (KHz) sampling frequency; 16 bits is the same format used to record CD-ROMs.

Tape drives can store from 4 GB to 40 GB of data per cartridge. They use 4 mm DAT or 8 mm DAT tape cartridges, both of which can store up to 40 GB. Tape drives interface to the PC using SCSI interfaces or IDE interfaces.

Sound Cards

All PCs today have the capability to create and record sound. Sound cards installed in the PC provide this capability. Early sound cards were mainly used to produce sounds for Windows activities and to play CDs. Today’s sound cards turn a PC into a programmable stereo system when it is connected to powered speakers. With the software and music data storage formats available, the PC becomes a programmable stereo system capable of producing three-dimensional sound. Sound stored in an MP3 format is greatly compressed. CD stereo music can be compressed by a factor of 12 compared to the files produced when sounds are directly recorded.

The original sound file format was a Windows Audio Volume (WAV) format used by the Creative Labs SoundBlaster sound cards. A more compressed format was a MIDI format. Some early music clips were recorded using that format. Most notably, Windows 95 and Windows 98 include several MIDI files useful in testing a PC’s sound capabilities.

The original PC sound cards represented sounds with 8 bits of data. This did not give the best sound representation. Sound cards soon evolved to 16-bit, 32-bit, 64-bit, and 128-bit capabilities. CD quality sound requires a minimum of 16 bits. The 128-bit sound cards are capable of studio quality sound—three-dimensional sound, if used with four speakers—and can synthetically reproduce 128 different multitimbre sounds. Special sound effects, such as reverberation, are also possible.

The original sound cards were ISA bus cards, but newer cards use the PCI bus. Typically, they have input jacks for microphone input, auxiliary input, and audio input that permit recording sounds at sampling rates varying from 5 kHz to 48 kHz. Output jacks are provided for line output, rear speaker output (on three-dimensional soundcards), and amplified output. Often, these cards support joystick ports and MIDI ports for games. Newer sound cards support digital audio format encoding and playing MP3 files, providing 5.1-surround sound, and Dolby® Digital 5.1 audio supporting digitally mastered DVDs. These cards connect to two, four, and five speakers. They decode and play Dolby® Digital 5.1 audio to provide 5.1-surround sound in movies, games, and music without the need for a Dolby® Digital 5.1 receiver. See Figure 1–16.

Figure 1–16 Digital sound card with stereo and mono sound plugs (in inset).

Dolby® Digital 5.1 audio, which is also called AC-3, is an audio encoding technique that compresses as many as six channels of digital surround sound into a single bitstream, reducing CD storage space. When decoded, Dolby® Digital 5.1 audio produces a maximum of six separate, discrete audio outputs. These outputs are left, center, and right channels located in front, providing precise dialogue positioning; two separate rear channels located behind, delivering ambient sounds; and a subwoofer/effects channel, providing deep bass. A combination of five discrete channels and one subwoofer is called a 5.1 speaker configuration.

LAN Adapters

Almost all business PCs are LAN connected. Many home PCs are networked as well using Ethernet, home wiring, or wireless LAN technologies. A LAN provides an easy mechanism for sharing disk drives and exchanging data between PCs. After people work with a LAN, they rarely want to go back to operating without the LAN. LAN connections bring high-speed Internet connectivity to the home. The bad news with LANs is that, when problems occur, the PC looks like it was frozen using liquid nitrogen. Because the PC’s operating system gives high priority to communication activities, it can become locked when the communications software connections disappear. A LAN connection requires a LAN card in the PC, cabling to other PCs with LAN cards, and networking software installed in all interconnected PCs. LAN cards are referred to as Network Interface Cards (NICs). Cable modems and Digital Subscriber Lines (DSL) connect into PCs using Ethernet LAN adapter cards. There were three early PC LANs: Datapoint’s ARCnet, the IBM token ring, and the Xerox-Intel-Digital Ethernet. Of these today, Ethernet is dominant and quickly evolving to meet the demand for increased transmission speeds that new applications place upon it. ARCnet has disappeared. A new LAN type, Asynchronous Transfer Mode (ATM), is also emerging for businesses. In the long run, it appears that Ethernet and ATM will become the dominant LAN types. LANs implement the electrical signaling on the LAN wiring and facilitate data transfer between equivalent NICs. Digital Equipment Corporation (now Compaq) marketed Ethernet LANs in 1982. It was one of the first LANs to interconnect PCs. In 1987, IBM delivered its token ring LAN. The first token rings were focused on IBM’s mainframe computers and PCs. The token ring still holds a significant market niche today. It is moving to higher speeds, but may be displaced by newer technology LAN and telephony NICs in the next few years as ATM technology takes root. Ethernet dominates the PC LAN market and is likely to continue to dominate it. Ethernet uses Unshielded Twisted Pair (UTP) wiring to interconnect PCs. This wire is classified by its electrical characteristics, with different types of wire capable of higher transmission speeds. The initial Ethernet wiring was a coaxial cable bus, which is seldom used any more.

This was not the same coaxial cable used for television, but a version having different electrical characteristics. Television coaxial cable was 75-ohm cable while Ethernet cable was 50-ohm cable. PCs using coaxial cable were connected in a simple bus configuration with coaxial cable running from one PC to another.

UTP cable soon replaced coaxial cable. Twisted pair cable required that each network PC be wired into a hub. The hubs electrically isolated each individual LAN-attached PC from the others so that, if a PC malfunctioned electrically, it did not crash the remaining PCs and the LAN. This improved overall network reliability. Most Ethernet PCs today connect to a switch. Switches provide the same capabilities of a hub and more. They increase Ethernet performance by isolating traffic between PCs from PC traffic.

Ethernet uses a Carrier Sense Multiple Access with Collision Detection (CSMA-CD) media access protocol. Each PC connected to the Ethernet broadcasts as needed. When its broadcasts collide with broadcasts from other stations, the Ethernet NIC detects this by an excess voltage drop on the cable and then computes a new time to attempt a rebroadcast of the corrupted packet. The new time is based upon previous collisions and is randomized within the rebroadcast time window.

UTP wire is classified into categories, with ordinary twisted pair telephone wire being classified as Category-3 wire that is capable of transmission speeds of 10 MB per second. Most Ethernet wiring installations use Category-5 UTP wire, capable of speeds up to 100 MB per second. New Ethernet LAN installations use Category-5 data grade cable (Category 5e or Category 5+) or Category-6 cable, which supports higher speeds. Ethernet is designed to run up to 1 GB per second across Category-5, Category-5e, Category-5+, or Category-6 twisted pair wiring and across fiber optic cables. The general rule is that the higher the speed means the shorter the wires that run between the hub and the PC.

Ethernet PC NICs are ISA 8-bit, ISA 16-bit, and PCI bus cards. The newer Ethernet NIC cards are all PCI bus cards that operate at either 10 MB per second or 100 MB per second and in half-duplex (one way at one time) or full-duplex (two way simultaneous) transmission modes. The new Ethernet cards automatically sense transmission speed and half- or full-duplex transmission capabilities. The token ring network also uses hubs to interconnect the networked PCs.

Similar to Ethernet, the hub isolates each station from the other stations on the token ring network so that PC and NIC malfunctions do not impact the other network stations. The token ring is different from Ethernet and must have hubs to work normally while Ethernet works in a simple bus configuration or in a hub configuration. Furthermore, the token ring hubs must be configured as a closed loop to form a ring and function properly. In the token ring token-passing protocol or Medium Access Control (MAC) operation, a token frame circulates from station to station. When a station has data to transmit, it marks the token frame as busy and appends data to the frame. The frame then circulates around the token ring; the destination station copies the data from the frame as it passes. If the data is copied successfully, the receiving station signals success by setting bits at the end of the frame. As the frame again passes the transmitting station, the transmitting station removes it from the ring and then reissues a free token so that succeeding stations may use it to transmit data they have.

Token ring networks operate at 4, 16, or 100 MB per second and will operate soon at 155 MB per second. The NIC cards have ISA 8-bit, ISA 16-bit, and PCI bus interfaces. IBM specifies token ring cabling as types, with the preferred token ring cabling being Type-1 or Type-2. The data-carrying pairs in these cables are two shielded twisted pairs. IBM Type-3 is equivalent to Category-3 UTP cable. Other token ring manufacturers use the Category-3 and Category-5 UTP cable equivalent to that used for Ethernet.

ATM NICs are beginning to emerge. The ATM technology promises to integrate LAN functionality and video telephony effectively into a single network connection. ATM has switches to switch data between interconnected PCs like a LAN, as well as between interconnected Wide Area Network (WAN) switches like telephony. ATM NICs transmit data at 25 MB per second, 155 MB per second, and 622 MB per second across Category-5, Category-5e, Category-5+, or Category-6 (when finalized) twisted pair wiring and fiber optic cable connections. ATM NICs interface to the PC through the PCI bus. Windows 98 comes with driver software and other software supporting ATM.

Modems

Dialup networking using modems provides Internet connectivity for many home PCs. A modem is basically a telephone for a computer. Modems modulate and demodulate digital data, converting it to analog voice-grade (0 Hz to 4,000 Hz) signals that travel across telephone channels. Modems are specified by their signaling technology, which in turn determines their maximum transmission speed. Table 1–5 lists the signaling specifications and related modem maximum transmission speed.