OTOY Forums

Hello everyone,
A (hopefully) quick hardware question:

We are building up new worstations and have 2 x EVGA GTX 980 Ti (superclocked) cards per workstation and i7 4790k.
The motherboard of choice is the Asus z97 Pro Gamer. (which we already have here)

It has 2x PCIe 3.0 X16 (single x16 / dual x8) slots and one PCIe 2.0 x16 slot which runs in x4 mode.
Do we lose performance in any noticable way because of the x16 x8 x4 thing if we use two cards?
And could we put in a third card without problems or losing performance on the that card? (would run on x4 mode)

Have to be honest, that I don't get the whole x16 x8 x4 thing - but want to make it clear before we unpack the mainboards and can't send them back.

Thanks!

already answered You on facebook, but here's a copy here:

lanes & their speed (gen2, gen3) only influence upload speed, rendering itself isn't, at all.

Now where You might end up loosing speed is on chosen cards - just because they have word "overclocked/superclocked" or whatever doesn't mean You are going more for You money - quite opposite actualy. Why?

Well, if You have space in between (placing cards at least a slot apart) & if You have good airflow in Your case, You might end up runing fine, but

..if You block airflow by placing cards side by side You will end up loosing performance due to insuficient airflow & lowered cooling capacity.

Non reference coolers are not meant for multi GPU rigs & backplate is no go if You're planing more than pair of cards in the future. Even manufacturers do recomend to go with reference design coolers if You plan having 3-4 cards.

so, upload speed will be influenced (but You would not feel it between x8 vs x16), maybe only on 4x with very heavy scenes. Rendering will be the same. But You might end up loosing a bit of performance due to heat circulating in Your case smile emoticon (as cards sips hot air again the cooling will not be as efficient). So what's the solution?

Go for reference design, save some money & invest those into getting better case & better fans, so Your cards would always have fresh air to cool down smile emoticon this way You minimise noise, lower operating temperatures because of that those cards will end up runing at higher speeds giving You more performance.

Hope that helps.

What I may add to Tom's recommendations:

Your motherboards is pretty good for 2 gpu layout on air - just don't use the lowest pcie socket for any additional card or you'll encounter heat transfer and throttling. With extra space between gpus you may go with latest asus 980ti strix with 2x8 power sections - they give you great power and OC even on air. But as Tom wisely mentioned - if you plan to expand to more gpus (4 with another mobo) you'd better go with a reference design 980ti that dissipate heat outside a case. Or you'll be advised to go with watercooling....

is it still the case that rendering speed isn't affected if the 2nd pci-e slot runs @4x?

thinking of building a Ryzen 5950x system with dual GPU for rendering (dual 3060 as i can't find anything else but would like to be able to upgrade when possible)

will a board with 2 x pci-e x16 where the 2nd slot runs at x4 suffice or do i need x8/x8 or better?

any MB recommendations?