Here are some important technologies pertinent to current and next-generation PCs, with a brief explanation of each:

ACPI

Advanced Configuration and Power Interface(ACPI) is the current standard for configuring system components under Plug and Play, monitoring the health of the system, and managing power usage. It replaces Intel's Dynamic Power Management Architecture (DPMA) and Advanced Power Management (APM). All current PCs and motherboards include at least partial ACPI support. ACPI is one of those technologies that isn't quite "here yet." When it works as it should, which is usually, it provides power management and other functions that many find useful. When it doesn't work properly, or when it conflicts with other technologies such as USB, it can cause very subtle, intermittent problems that can have you pulling out your hair. It can also cause very nonsubtle problems, including systems that go into a coma rather than suspending, screens that refuse to unblank even though the system itself is running, and so on. In general, when we encounter a system that hangs or otherwise behaves strangely, our first suspects are the power supply or the memory. But ACPI conflicts are also high on the list.

AGP

Accelerated Graphics Port(AGP) is a dedicated video port connector, introduced in 1997 by Intel and now nearly ubiquitous. In theory, AGP improves video performance by removing it from the 33 MHz PCI bus and by allowing a video adapter to use main system memory. In practice, all high-performance video cards (PCI or AGP) have a large amount of fast, local video memory. Video performance is constrained by the bandwidth between the graphics processor and video memory. These cards render images in local video memory rather than in main system memory, so the limited bandwidth of the PCI bus is not a bottleneck. AGP video cards do not fit PCI slots, or vice versa. AGP is fully supported under Linux, Windows 98, and Windows 2000 or later (but not under earlier Microsoft operating systems). Note that many motherboards now use AGP 2.0-compliant 1.5V AGP slots that do not support legacy 3.3V AGP cards, so if you're upgrading a motherboard you may also have to upgrade your video adapter.

IAPC

Instantly Available PC (IAPC) is an Intel initiative that defines power-saving modes that retain the ability to respond to programmed or external triggers, such as LAN activity (Wake-on-LAN, WOL) or an inbound telephone call (Wake-on-Ring, WOR).

Plug and Play

Plug and Play is a joint Intel/Microsoft specification that allows computers and peripherals to configure themselves by negotiating for available system resources. Full implementation of Plug and Play requires that the chipset, BIOS, operating system, and devices all be Plug and Play-compliant. Ideally, adding a device in a Plug and Play environment requires only physically installing the device. Plug and Play then configures everything automatically, loading the appropriate driver and assigning nonconflicting resources (IRQ, I/O port, DMA, and memory space) to the device. In practice, Plug and Play sometimes does not work properly. Plug and Play is partially supported by early releases of Windows 95, and fully supported by Windows 95 OSR2+, Windows 98, Windows 2000 or later, and Linux.

UDMA/100 and /133

Ultra DMA/100 (UDMA/100) and Ultra DMA/133 (UDMA/133) are recent standards that support IDE hard disk data-transfer rates up to 133 MB/s, eight times those supported under earlier Programmed I/O (PIO) modes, four times that of UDMA/33, and twice that of UDMA/66. UDMA (Ultra Direct Memory Access) modes have low CPU utilization under heavy disk load (typically ~1.5%, versus 80% for PIO), and high-end UDMA drives approach low-end SCSI drives in raw performance. The fastest current ATA hard drives can barely saturate a UDMA/66 interface, so the advantage of UDMA/100 and UDMA/133 over earlier UDMA standards is small for now. But we expect new-generation hard drives to ship in 2003 and 2004 that will saturate UDMA/66, so UDMA/100 is worth having. UDMA/100 is supported by most current systems and motherboards, and by many current IDE drives. Many current motherboards do not support UDMA/133, which is not yet a formal standard, although some motherboards shipping during 2003 will incorporate it. UDMA can be used with all versions of Windows 95/98/Me, by Windows NT/2000/XP, and by Linux, although configuring it is non-trivial in some of those environments.

The Big Drive Interface Initiative

The ATA standard has used 28-bit addressing since its inception. When using standard 512-byte blocks, a 28-bit address limits maximum drive size to 128 GB. Until 2001, that was so large as to be no limit at all, but the exponential growth in hard drive sizes has now put them hard against that 128 GB limitation. In 2001, a consortium of storage industry companies, led by Maxtor, introduced The Big Drive Interface Initiative. This initiative replaces the old ATA interface with a new version that uses 48-bit addressing, which allows drive sizes up to 128 petabytes (PB), still using standard 512-byte sectors. The new interface is backward-compatible with older drives, and the newer drives are backward-compatible with older interfaces (although, of course, you are limited to using 128 GB of the drive's capacity if it is connected to an older interface). As this is written, only motherboards based on the most recent chipsets have embedded 48-bit ATA interfaces. Nearly all new motherboards produced in 2003 and 2004 will include 48-bit ATA interfaces, although the ATA interface is being phased out in favor of the new Serial ATA interface. For more information about The Big Drive Interface Initiative, see http://www.maxtor.com/en/technologies/big_drives/index.htm.

USB

Universal Serial Bus(USB) is a general-purpose communications interface for connecting peripherals to PCs. USB 1.1 supports speeds up to 12 Mb/s. USB 2.0, finalized in February 2000, supports speeds 40 times faster—up to 480 Mb/s. USB 2.0-compliant interfaces and peripherals began shipping in late 2001, and are now commonplace. USB is royalty-free and strongly backed by Intel, which makes it likely to prevail over the competing, more expensive IEEE-1394 FireWire standard. USB will ultimately replace low-speed "legacy" serial, parallel, keyboard, mouse, and floppy interfaces, and may also become a standard or at least alternative interface for mid-speed devices such as video, network adapters, and optical drives. All recent systems and motherboards include at least USB 1.1 ports, and nearly all include USB 2.0 ports. USB 1.1 is fully supported by Linux, Windows 98, and Windows 2000/XP, but not by earlier versions of Windows. USB 2.0 is fully supported by Windows 2000/XP and recent Linux releases.

An exhaustive list of these and other PC technology standards is available in the PC 2001 document and on the Web at http://www.pcdesguide.org/pc2001/Resources.htm.