new to SLI, just a couple of quick questions

[cayn99]

hi everyone,

i was thinking to build a new Pc soon, since i'm going to use it mainly for renders i was planing to stack some nvidia cards. But honestly i'm very new to SLI so i'd like to ask a couple of quick questions to the expert users;

let's say i've built a machine with a 4 way sli, a huge sandwich of 4 gtx xxx, my concerns are all about the "main" video card, i mean, sorry if it may sound very noobish but...out of the 4 cards that i have in my pc, 1 of them is supposed to be used by the system to actually...work as a video card, display graphic, editing ...?

does it means that octane is not using it to render?

if so, i would rather use a cheaper card as system video card or a dedicated one for 3d editing, like an old quadro (just guessing i've no idea if adding in stack a different model is going to kill the render performance of the remaining 3 cards)

if so, can i use an old ati card to run only as system video card? (blasphemy? ^^)
i mean if octane only consider video cards as cuda devices, 3 are going to be cuda and the system video card wont

sorry my concerns may sound ridicolous to expert users, but so far i only used octane with a single gpu, thanks in advance.

[FooZe]

Hi Cyan99,

The card that your monitor is connected to will be your primary one.
This will be used by windows and anything else that uses the primary display.
Octane can still use this card, but generally it is a better idea to use it for display only.
If you use it for rendering as well, then you will need to be careful of a couple of things:
1) It might start causing display lag because of the heavy load octane will be putting on it. (we have added a priority setting to octane recently that can help but it's not 100% flawless).
2) If a lot of the cards VRAM is being used by the OS, this will lower the amount left for octane, and therefore your max scene size (since octane is limited to the smallest of the cards used for render).

I'm not sure how happy ATi and NVIDIA cards are to live together (especially drivers). I know for the 3ds max plugin at least this will cause problems.

Thanks
Chris.

[cayn99]

hi there,

thanks a lot for the infos, i think i'm going to do as you suggested, i'll keep 1 card for display only; to do this, uhm...inside the case, the card that i want to keep as system card shouldn't be connected to the others with the SLI cable right? or it should be connected but that's enough to exclude it via software?

[FooZe]

Hi,
Octane does not use SLI so it doesn't need the GPU's to be connected (or even the same type).
In octane, the GPU's are seen as CUDA compute devices, so you can always just turn them off or on as you want from octane.

If you want SLI for games, then things get a little more tricky.
You will need to connect the 3 similar/identical cards with the SLI connector and then disable Multi-GPU in the NVIDIA control panel when using octane.

Also, when you want to game with SLI you will need to plug your monitor into one of the 3 gaming cards.

Thanks
Chris.

[cayn99]

hi there,

thanks again for the quick reply, i think i have enough elements now, thanks for the clear explanation