I am looking at potential motherboards for a computer I want to build and ran into this conundrum. The motherboard has two PCI Express slots that allow for 16 channel cards to fit in them. The catch is only one of them operates at 16 channels, the other operates only 4 channels.

My question is, would it be faster to buy a PCI Express graphic card and install it in the 4 channel PCI Express slot? Or would it be better to buy a standard PCI graphic card and install it in one of the available PCI slots?

  • Many motherboards also listed 2-3 16lane capable slots, and the lanes are shared anyway. It is only recently that the stats At some places identified just how that all works in reality. Some newer boards do support 2&3 real 16lanes, but no surprise it is through a sort of "hub" on the motherboard. Check out the processor "architecture" and see more of how that (kind of) starts out . 16 vs 8 lanes for todays common uses is a minimal change. You can certannly find 8&8&1 vrses a 16&4. I dont know enough about it, just seeing the trend. The CPU has a set number, the boards connect them different – Psycogeek Apr 11 '12 at 17:49
  • ...They still make standard PCI graphics cards? – Bigbio2002 Apr 17 '12 at 18:55
  • According to websites like NewEgg, yes. Or at least they are sold still – Stephen R Apr 17 '12 at 19:32

Conventional PCI (of the type you find in any home PC) is capable of transferring 133MB/s (megabytes per second), there are server class versions that work at higher data rates but those are not common for home users.

PCI-E v1.x on the other hand is able to transfer 250 MB/s (2.5 GT/s) per lane so a PCI-E x4 card will be able to transfer of the order of 1000MB/s. Higher versions of the PCI-E standard can transfer more, as an example V2.0 can transfer 500MB/s per lane.

So it will, as a home user, always be better to get a PCI-E card, even if it is only x1.

  • Yeah after poking around a bit I found out the truth of PCI Express vs Conventional PCI. If I understand correctly, x1 PCI Express v2.0 is about the same speed as conventional PCI - but seeing as I have 4 channels available in this scenario...the clear winner is PCI Express. The hardware capacity of PCI Express cards also beat the heck out of PCI so another reason to go with PCI Express – Stephen R Apr 11 '12 at 17:47
  • Even x1 PCI-E V1 (250MB/s) is about twice as fast as PCI (133MB/s). You are not likely to find the faster PCI standards in a home PC so I only listed the base speed. PCI-E V2 is twice as fast as PCI-E V1 so a single lane is nearly 4 times the speed of a standard PCI bus and x4 is faster still. – Mokubai Apr 11 '12 at 17:52
  • I figured 64 bit PCI slots were being used at this point since the form factor has been around a while. Thought they would have at least been upgrading them as time goes on. In the case of standard PCI slots only being 133Mhz, I am completely sold on PCI Express x4 being much faster than PCI – Stephen R Apr 11 '12 at 18:02
  • I think for desktop boards compatibility and cost won out over performance. 64-bit needed a larger connector, a lot more PCB traces and a lot more pins on the host chip. Higher clock speeds needed a 3.3V bus voltage which would break compatibilty with older cards. So desktop motherboard stuck with the basic 5V 33MHz 32 bit version throughout PCIs life. – plugwash Jun 7 '17 at 14:44

The PCI Express x4 by far. PCI ( regular ) is very slow even compaired to a PCI Express x1 slot. PCI Express 1.0 x4 slot has a bandwidth of 1.0 Gbps while a PCI slot maxes out at 266 Mbps. Later versions of the PCI Express bus double the transfer rates of version 1 allowing up to 4 Gbps with version 3 in a x4 slot.

  • After browsing around for PCI cards in the possibility that using one was faster than a PCI Express card, I found that PCI cards have a serious lack of hardware compared to PCI Express. I will have to look up in my A+ book to see the details on speeds for individual channels on PCI Express. – Stephen R Apr 11 '12 at 17:34

From This wikipedia article...

As a point of reference, a PCI-X (133 MHz 64-bit) device and PCIe device at 4-lanes (×4), Gen1 speed have roughly the same peak transfer rate in a single-direction: 1064 MB/sec. The PCIe bus has the potential to perform better than the PCI-X bus in cases where multiple devices are transferring data communicating simultaneously, or if communication with the PCIe peripheral is bidirectional.

So, if the PCI video card you purchase is a PCI-X card, and the PCI slot you use is a PCI-X slot, then it is possible for it to be as fast as a PCI-E x4 video card. But, this in a perfect world under perfect circumstances.

In general, PCI-E is an improvement over PCI in every way, and you should expect PCI-E video cards, even in a PCI-E x4 environment, to out-perform older, standard PCI video cards.

  • I have only seen PCI-X cards for server grade stuff mainly raid cards etc. Haven't seen any graphics cards take advantage of the improved bus only the older PCI 32bit. – Lamar B Apr 11 '12 at 17:38
  • When did PCI X come into the equation? – Supercereal Apr 11 '12 at 17:56
  • Only as a point of reference. There is no mention of the specific motherboard, so there is no reference to the specific details regarding the PCI slots on that motherboard. I simply supplied existing information, and then summarized based on what the user could expect. – Bon Gart Apr 11 '12 at 17:59

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