A quick overview of the PCI-X bus slot interface

PCI-X (Peripheral Component Interconnect Extended) is a computer bus and expansion card standard which was designed to supersede PCI. To be more accurate it is a revision enhancement of PCI that increases clock speed and hence the amount of data exchanged between the computer processor and peripherals. Spectrum PCI-X cards run at a 66MHz speed, not as high as the theoretical maximum possible on PCI-X, but still providing a rate approximately double the 100-120M Byte/second data throughput obtained with the PC when compared to standard 33MHz PCI. This is a big advantage for signal instrumentation card running at high speeds and requiring real-time transfer. Motherboards with the PCI-X slot are becoming less common now and usually targeted at server systems. Here is a link to one such supplier with desktop and 19" rack mount chassis options:- http://www.supermicro.co.uk/products/motherboard/

Note that a card running 66 MHz installed in say, a PCI-X 133 MHz bus, will force other cards to the lower clock rate, so if you already have a card installed capable of using the 133 MHz speed (for example a RAID controller) on the same PCI-X bus segment, it will work, but will have to work at 66MHz and share the total bus bandwidth. To get around this limitation, motherboards can have separate PCI-X channels, with dedicated controllers, thus allowing for better multi-card compatibility. If you would like to use multiple cards in the same PC we can help recommendations, in particular looking at the possibility of using PCI-Express card instead, as these use slots that do not share the same bandwidth and get around the second problem of the dwindling availability. PCI-X is sometimes confused with newer PCI-Express interface, commonly abbreviated as PCI-E or PCIe. While they are both high-speed computer buses for connection of cards, they differ in a number of ways and are not compatible

PCI-X cards are backwards compatible and can hence be used with PC's with the older PCI slots.

For a more detailed examination of PCI-X; http://en.wikipedia.org/wiki/PCI-X

DataQuest Solutions Ltd August 2013
Last modified 24/02/14