Overview

Computer technology continues to advance with breathtaking speed in accordance with Moore's ^[1] Law, among other things. A new computer is nearly obsolete as soon as you take it out of the box. Since Intel first defined the PCI bus back in 1992, memory bandwidth requirements in virtually all computer systems, whether they be high-end servers or home PCs for game playing, have increased by orders of magnitude. What started out as a 32-bit, 33 MHz bus with a bandwidth of 132 Mbytes per second was first expanded to 64 bits and then to 66 MHz. The maximum bandwidth of a 64-bit, 66 MHz system is thus 528 Mbytes per second. This insatiable demand for bandwidth led to the development of PCI-X, an extension to the PCI standard that boosts maximum bandwidth to 4 Gigabytes per second.

Today's computer systems, with their emphasis on high-resolution graphics, full-motion video, high-bandwidth networking and so on, go far beyond the capabilities of the architecture that ushered in the age of the personal computer in 1982. Modern systems demand high-performance interconnects that also allow devices to be changed or upgraded with a minimum of effort and technical knowledge by the end user.

In response to this need, PCI (Peripheral Component Interconnect) and a subsequent major enhancement, PCI-X, have emerged as the dominant mechanism for interconnecting the elements of modern, high-performance computer systems. It is a well thought out standard with a number of forward-looking features that should keep it relevant into the...