Non SLI dual Nvidia cards & Cycles?

So, is anyone running non SLI dual Nvidia cards? Isn’t there supposed to be be support for dual cards now, didn’t I read that somewhere? But what works, which configurations works with Cycles and how can I set it up? What’s possible?
1: Card one or two only without SLI
(yes, according to the wiki)
2: Card one and two together without SLI
(not yet ,according to the wiki)
3: Card one and two together with SLI
(no info in the wiki, but isn’t that a hardware thing and should work automagically?)
The last one there isn’'t really interesting for me, not in this moment anyway, but as it might be for others, I put it out there… :smiley:

What bothers me is that GPU-rendering locks up the Blender GUI and generally hogs the machine, so I’m thinking of running dual cards, one for OGL & running the monitor and all that + one for pure CUDA… But it would be really nice being able to run them in parallell for specific renders… So, who’s gonna tell it as it is? ;D

You don’t need SLI to use multiple CUDA devices and having it active is actually detrimental to performance, or so I’ve heard. You can have multiple GPUs rendering in parallel in recent builds, although the scaling/load balancing is not that good (There are some benchmarks somewhere on the forums). You should absolutely have two cards of the same speed, or else your render will actually be slower. The wiki is probably outdated on that matter.

I have two GTX 580 cards in my rig, and I can run either one individually or both together. The scaling when using both is not 100%, more like an 85% increase - which is still significant. I get about a 99.9% upscale in Octane when using both cards, so I imagine that eventually Cycles will improve in scaling performance - or at lease the potential appears to be there.

I actually have run both Octane and Cycles with SLI still active on my cards and not experienced any noticeable performance degradation. That may not be true with other types of cards and driver combinations, or in every possible scenario though. Thats just been my experience. It’s probably best to deactivate SLI when rendering as recommended.

Just walked in the door not five minute ago, a 560Ti 2Gb in hand, hehe… So now I’ll play around and see what difference it makes, single, double, all that… If I get it running - I’m not 100% sure I’ll have enough free molex connections to get power to the second card, time to log out & find out though… ;D

So, no, I did not have enough free connections to power the card, I need sata->molex converters and it first seemed no-one had these in stock locally, but after making a few calls I actually located some quite close and now I got both cards in my home box.

And using them separatly is very Nice. The 560Ti is faster on rendering and I still have my awesome GTX285 for OGL and video editing, really nice.

About using both cards for rendering, seems OpenCL is generally way slower & using both cards, Cycles seem to render slower than using either card in CUDA. Also, using a glass shader seems to kill Blender instantly when starting to render image (f12) even though rendering seems more stabile when done in viewport… Basically OpenCL, as expected, seem very unstabile and thus not really interesting for me…

So now the question is, shall I keep this config? $200 for a setup that only works for Blender/Cycles, I have no other need for it. Also, what is actual need and what’s that stupid need for any new hardware, hehe…? ;D