PCI Express x16, PCI Express x4 (x16 connector)?


I'm looking at buying a pre-built pc (/ducks) and the MB specs listed show the following:

PCI Express x16, PCI Express x4 (x16 connector) and 3 PCI slots.

I've never built a SLI/CF box before so I'm not quite sure of all the specifics. My question is what limitations will I see running CrossFire on a PCI-e X4, with a X16 connector?

I was told that this board is x-fire ready. But I'm thinking that may not mean x-fire will work as wel as if ther were 2x16's, at least thatt is what I'm assuming.

So, is a X4 slot with a x16 connector normal for x-fire or should I be looking at a MB with 2 X16 slots?

Thanks in advance
7 answers Last reply
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  1. I think normally, the 2 x16 connectors will either share a single x16 lane (nF4, ATIX200) or the newer chipsets give each connector its own x16 (ATIX3200, nF5/6)

    I've never heard of one that did x16 on one and x4 on the other, although x4 connector is the same as x16 connector. What motherboard is it again?
  2. they're quite common actually. though the other slot is x16, it has x4 lanes. the advantage is you can buy a x16 or x8 RAID card (for example) and it'll fit nicely. not many motherboards have x8 and x4 connectors... so putting a x16 connector is a good solution. raid cards don't need more than x4 bandwidth.

    i wish more botherboards had an extra x16 connector w/ 4x lanes. that way i can run SLI and have a high performance RAID card.
  3. thannks for the replies. The MB specs can be found here: http://www.gateway.com/programs/fx530/index.asp?page=techspecs

    it is an oem BTX 5-slot Intel® 975X motherboard.

    my concern is that even if the pipes are reduced to 8 per card, i'll only pump 4 on the x4 connector. If that is the case i'd like to understand how much of a performance reduction, if any, it will be.

    thanks for any insight.
  4. i don't know of any MODERN articles that compare the difference in performance between x4 and x8. however, there is this article published a couple years ago:


    as you can see there are minor differences in speed between x4 and x8. however, keep in mind they're testing the 6800 series cards. the performance gap has likely increased quite a bit since then, especially with the latest 79xx series and definitely with the 88xx series.

    my advice: don't bother with SLI on a x4 connection.
  5. Quote:
    i wish more botherboards had an extra x16 connector w/ 4x lanes. that way i can run SLI and have a high performance RAID card.

    i believe the quadfather motherboard has that, 4 actually, but your supposed to use them for physics
  6. oh i know they exist... just saying i wish there were more. but you're right, there will be more when physics goes mainstream.
  7. Awesom info, thanks again for you help, mpjesse.
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