PC Hardware in a Nutshell, 2nd Edition

1.1 PCs Defined

Who decides what is and what is not a PC? That question is not as trivial as it sounds, because there has never been (and probably will never be) an all-embracing de jure standard to define the PC. IBM created the de facto PC standard (and trademarked the name) when they shipped the first IBM Personal Computer in 1981. For more than five years, until their introduction of the ill-fated proprietary PS/2 line in 1987, IBM defined the PC standard. For a short time thereafter, some considered that Compaq defined the standard. But the days when any PC maker defined the PC standard are far in the past.

These days, Intel and Microsoft jointly define the de facto PC standard. In fact, a good working definition of a PC is a computer that uses an Intel or compatible processor and can run a Microsoft operating system. Any computer that meets both requirements—a so-called Wintel computer—is a PC. A computer that does not is not. Computers based on some Intel processors cannot run any Microsoft operating system, and thus are not PCs. Conversely, some computers with non-Intel processors can run Microsoft operating systems, but also do not qualify as PCs. For example, DEC Alpha minicomputers running Windows NT 4 are not PCs.

Two formal documents, described in the following sections, define the joint Intel/Microsoft standards for systems and components you are likely to be working with. These standards are de facto in the sense that system and peripheral makers are not required to comply with them to manufacture and sell their products. They might as well be de jure standards, however, because compliance is required to achieve such nearly mandatory certifications as inclusion on the Windows NT/2000/XP Hardware Compatibility Lists.

1.1.1 PC 99 System Design Guide

PC 99 System Design Guide (PC 99) is a book-length document that defines required, recommended, and optional (neither required nor recommended, but must meet the standard if included) characteristics for several classes of PCs, including Basic PC 99 (further subdivided into Consumer PC 99 and Office PC 99), Workstation PC 99, Entertainment PC 99, and Mobile PC 99.

PC 99 is the penultimate member of a series of documents, which began in 1990 with the first MPC standard, and continued with the PC 95, PC 97, and PC 98 revisions. PC 99 was formalized in mid-1998, took partial effect in July 1999 for systems to be delivered in Q4/99, came into full effect 1/1/00, and defined the standards for systems and components delivered through late 2001.

In some ways, PC 99 was unrealistically far ahead of its time: for example, in recommending Device Bay and 1394 as standard storage interfaces. In other ways it was far behind: for example, in requiring only a 300 MHz processor and 32 MB of RAM for some configurations. Some portions are skewed to Intel CPUs (e.g., an L2 cache requirement was cut from 512 KB to 256 KB when Intel shipped Coppermine Pentium III CPUs with 256 KB L2 cache—probably not a coincidence), while many others are skewed toward Microsoft operating systems. Neither of those is surprising in the document that defines the Wintel standard. All of that said, PC 99 was and remains an important document because it defined the direction of PC development as we entered the new millennium.

You can purchase PC 99 in book form (Microsoft Press, 1998). You can view or download PC991.0 in Acrobat format (http://developer.intel.com/design/desguide/) or PC99a—the final release of PC99, with minor updates and corrections—in compiled HTML help format (http://www.microsoft.com/hwdev/platform/pcdesign/desguide/default.asp). The PC Design Guide home page (http://www.pcdesguide.org) also contains links to these documents in various formats.

If you've ever crawled around under a desk trying to read the tiny icons on port connectors, you'll appreciate one very visible manifestation of PC 99 compliance—standard colors for port connectors, listed in Table 1-1. Nearly all PCs and peripherals shipped since Q4/99 use these colors.

Table 1-1. PC 99 recommended connector color codes

Connector	Color		Connector	Color
Analog VGA	Blue		PS/2-compatible keyboard	Purple
Audio Line-in	Light Blue		PS/2-compatible mouse	Green
Audio Line-out	Lime		Serial	Teal/Turquoise
Digital monitor/flat panel	White		Speaker out/subwoofer	Orange
IEEE 1394	Grey		Right-to-left speaker	Brown
Microphone	Pink		USB	Black
MIDI/gameport	Gold		Video Out	Yellow
Parallel	Burgundy		SCSI, LAN, telephone, etc.	Not defined

1.1.2 PC 2001 System Design Guide

The PC 2001 System Design Guide (PC 2001) is, according to Intel and Microsoft, the final document in this series. In many respects, PC 2001 is more an addendum to PC 99 than a self-supporting document. Many PC 2001 specifications direct the reader to PC 99 and state only that the PC 2001 requirements are identical to those of PC 99, or are similar to those of PC 99 but with minor changes specified. The major differences between PC 99 and PC 2001 are:

• PC 2001 eliminates the strong emphasis of PC 99 on market classifications—Basic PC, Consumer PC, Entertainment PC, and so on—although it does specify different requirements for workstations and mobile PCs where appropriate.

• PC 2001 no longer categorizes components and functionality as "recommended," instead specifying only those that are required. A component or function that is not required is not mentioned. Some requirements, identified as "if implemented," are conditional. If a manufacturer provides that component or feature, it must comply with the specified standard.

• PC 2001 eliminates some former requirements because Microsoft and Intel deem them no longer important to the industry or "no longer relevant in defining the optimal user experience with the Windows operating system," whatever that means.

• PC 2001 defines requirements intended to support new and forthcoming technologies implemented in recent Microsoft operating systems, including Windows 2000, Windows Me, and Windows XP.

• PC 2001 places a greatly increased emphasis on legacy-reduced and legacy-free systems. Some "legacy" items, such as ISA expansion slots and device dependence on MS-DOS, are forbidden entirely, while others are merely strongly discouraged.

• PC 2001 emphasizes (although it does not mandate) features collectively called the Easy PC Initiative, which focuses on ease of setup, use, expansion, and maintenance.

You can download a copy of PC 2001 in Word, PDF, or Microsoft Compiled Help format from http://www.pcdesguide.org.