terminology - PCI, PCIe and PCI-X

[bernieL0max]

I am writing this post in an attempt to educate people to use the correct terminology when referring to PCI, PCIe and PCI-X Buses;


PCI is the 32-bit parallel bus we've had in our PCs and Macs for many years (10?)... the PCI bus has transitioned through 33MHz to 66MHz. It looks like this;

We've all no doubt seen PCI slots before; most of our internal Pro-Audio sound cards use the PCI bus. The PCI bus has enough bandwidth for our needs; I imagine this will be reason enough for manufacturers of Pro-Audio gear to hold off on transitioning to any new standard at least in the short term. But I digress; this is not the intent of this post...



PCI-X NOTE: THIS IS NOT PCI EXPRESS. PCI-X is a 64-bit extension of the existing PCI bus, used primarily in servers and high-end workstations. Apparently it also features in some high-end Macs? PCI-X is used for SCSI, RAID, Fibre Channel & LAN Cards which require a great amount of bandwidth to the processor. PCI-X works at 66MHz, 100MHz or 133MHz. It's slot look like a PCI slot with an extra bit tacked on the end - it looks like this because that's exactly what it is! This picture is a good comparison of PCI-X to PCI;



PCI-X 2.0 NOTE: THIS IS STILL NOT PCI EXPRESS. This standard was released on the same day as the PCI Express standard. PCI-X 2.0 builds on the existing PCI-X standard and ramps bus speeds up to 266MHz and 533MHz. The PCI-X 2.0 slot looks identical. Again, to recap; PCI-X is intended for servers and high-end workstations.



PCIe is the acronym for PCI Express PCI Express is the new standard for connecting devices inside a PC. PCIe is a serial bus. At this point in time PCIe is used primarily for video adapters, but this will change as manufacturers adopt the specification for addon cards. The PCIe bus has been designed so that multiple channels can be grouped together to increase bandwidth, these are referred to as PCIe x2, PCIe x4, PCIe x8 and PCIe x16 (etc). A single PCIe x16 connector is commonly found on new motherboards for the video card, along with a number of single channel PCIe slots.

I have already seen some server/workstation boards with PCIe x8 slots for future expansion - although personally I am yet to see any card that utilises this slot.

PCIe slots look like this;

This image shows a PCIe x16 slot, 2 single channel PCIe slots and 2 PCI slots (L to R).



Personally, I think PCI SIG - the group responsible for creating the standards, specifications and naming were a little bit lapse when naming 2 very different standards far too similarly (PCI-X and PCI Express). But, what's done is done... now we all just have to be careful to use the right acronym/naming when referring to any of these standards! :)



This post was slapped together, I might edit it to include a few more facts and specs when I get a chance...



And, just one last time for those at the back who weren't listening... PCI-X is NOT PCI Express! :)


Matt

[max cooper]

Originally Posted by bernieL0max

And, just one last time for those at the back who weren't listening... PCI-X is NOT PCI Express! :)


Matt

Nice going! I think a lot of people have been calling 'X' express. Although I think the organisation who is responsible for naming this stuff (there is one, I can't remember what they're called) was a bit tipsy when they created this easily confusable nomenclature.

[bernieL0max]

as i previously mentioned... PCI SIG is the group responsible for all things PCI...
www.pcisig.com

and yes... they were smokin something funny that day

[bernieL0max]

seems this is going to need a bump every now and then as ppl start confusing themselves and others again...