Single GPU & PCI-e 8x or 16x needed?

Hi, Crew-
I'm thinking the Gigabyte GA-P55A-UD6 is my new motherboard of choice for my i7 860.

A reviewer of this motherboard over at Newegg posited that a single GPU (in this case a Zotac GTX 275 Amp!) suffers a HUGE decrease in performance when limited to an 8x PCI-e channel instead of the usual 16x channel; and that Toms has the evidence to back it up. Where is this review as I can't seem to find it? (and anything at or anywhere else would be useful, too).

[n.b. on the UD6 the main PCI-e is limited to 8x on the 16x slot when USB 3.0 & Sata 6Gb/s is enabled]

5 answers Last reply
More about single needed
  1. USB 3.0 and Sata 6Gb/s aren't worth the tradeoff regardless. :P Most reviews show they only provide a minimal performance increase unless you need the extra speed for something very intensive and specific, like workstations I suppose. Is there a special reason you need to have those features at the expense of the full PCI-e slot?
  2. Well, correct me where I'm wrong, but I always understood that the bandwidth in the PCI-e 2.0 lanes vastly outpaced the throughput of the GPUs (except maybe the top-ended GPUs). If this is true, then I can have my cake & eat it too by having Sata 6Gb/s, USB3.0, as well as enough PCI-e bandwidth for a single GPU when playing games. Of course, if 8x in the 16x 2.0 slot isn't enough then I'll have to pick my poisons (and USB 3.0 & Sata 6Gb/s can be disabled in the BIOS thus bringing the board back to full 16x and 8x in the two 16x 2.0 slots, respectively).

    I'm ready to upgrade to a Core i7 and don't wish to wait any longer (but don't want to feel an urgency to upgrade once USB 3.0 & Sata 6Gb/s start to saturate the market).

    So, anyone have an article or two?
  3. Answering my own question, it appears 8x (2.0) from 16x debilitates a GPU performance roughly 2%:

    (original article: )

    In fact, it appears 4x (2.0) is totally sufficient to get the majority out of the PCI-e lane.

    Anyone have any evidence to suggest 16x (2.0) is necessary for a single GPU system versus 8x?

  4. A bit older of a review, but 'confirmed':,1915.html

    Anyone see anything more recent?

    (showing the 8x scores are similar to the same CPUs running at 16x)

    The evidence appears overwhelming, at least at this stage in GPU development. No?
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