Nutshell Comparison of PCI, PCI-X and PCI Express.

Purpose: I looked at the different I/O bus standards to improve I/O performance of one of my systems. I wanted to figure out what's the next step up from PCI. Here is a summary of the standards.

Definitions

PCI

Peripheral Component Interconnect, a bus for connecting peripheral devices (IC's or add-on cards) to motherboard.

PCI

The original standard. 33 MHz 32 bit bus, peak transfer rate 133 MB/s.

PCI-X

Variation on the original: the bus faster and wider and slightly different protocol.

PCI Express

Next generation architecture. Point to point topology, rather than a shared bus. Each point-to-point connection is called a "link", and a link is composed of "lanes". Each lane is composed of two lines, one upstream, one downstream. A single lane can transmit 2.5 Gbps in each direction; with a sustained transfer rate of 250 MB/s. You can have multiple lanes in a link. The multiples are 1x, 2x, 4x, 8x, and 16x. The more lanes you have, the longer the PCI Express slot. Lanes are fixed in the motherboard, you can't add or remove lanes.

References:
• http://en.wikipedia.org/wiki/Pci
• http://en.wikipedia.org/wiki/List_of_device_bandwidths
• http://www.pcstats.com/articleview.cfm?articleid=3D1087&page=3D1

Up to: Aleksey's tech notes