Folding Forum

Hi there,

I'm using a GA-Z170X-UD3 mainboard with two GPUs each connected with pcie 3.0 x8.
There is still one pcie x16 slot running at 3.0 x4 available.

Some say that I can use only 2 GPUs because Skylake can use only 16 pcie lanes...
Is it possible to run a third GPU (with 3.0 x4) in this available slot?

Thanks

The info iI have on Skylake says it can run 28 to 44 PCIe 3.0 lanes. I don't think you're going to have a problem as long as you use a GPU that fits in a single slot. (though cooling may be a problem. That's probably a lot of heat for the fans you have.)

Bruce I think 28 to 44 pcie lanes is haswell CPU with x99 chipset. The Skylake CPU is 16 lanes and the chipset Z170 supports pcie x4 lanes additional.

The mainboard manual says the pcie x4 is not shared with the other two pcie x8 slots. Normally this is used e.g. for a pcie SSD. But this should work for an additional GPU too. My only concern is that a GPU cannot be initialized in this x4 slot but I guess it can.

The space between x4 and the x8 slot is more narrow than between x8 and x8 so cooling could be more difficult with 3 GPUs using high watt.

If you put in a fast GPU there is a pcie x4 bottleneck on Windows. Linux doesn't matter much.

Thanks for your answers. Then I will give it a try.
I use risers to have the GPUs outside of the case for cooling reasons.

A few months ago I made a comparison on a 1080 Ti between x16, x8, and x4.
x16 and x8 was about same speed, but on x4 a 1080 Ti gained only about 80% of x8/x16.

I've got 1080 ti cards on my Asus Prime Z270-a and Asus Prime Z370-A boards. Both boards have 3 GPUs each. There is no noticeable loss of speed on the third card.

TLS2000 wrote:I've got 1080 ti cards on my Asus Prime Z270-a and Asus Prime Z370-A boards. Both boards have 3 GPUs each. There is no noticeable loss of speed on the third card.

Running which OS? That does make a difference.

And which WUs? I'd assume that because GPU utilization on a 1080 Ti on Windows is less than 85% only for 9xxx WUs, and >90% on 11xxx that this could also make a difference

Linux, good shielded pci-e riser, some case modding (or TT Core71, or FD Define R6) or open frame makes triple (or more) card rig high effective
viewtopic.php?f=38&t=30155#p296621
Mobo mentioned has good pci-e lines distribution.