nvidia cards and sli

maybe it s a stupid question but… if i got 2 card a gts 250 and gtx 460 can i put both in the same computer and get a benefit with renderer like octane? or should i get the same 2 cards. Is ther something to do in the bios?
here is the rig i plan to get
7-930 @ 4x 3600 Mhz Coolermaster V8 Cooler
6 GB DDR3-1600 Ram
500 GB Sata HDD
GTX460 1024 MB Nvidia DirectX 11, Cuda, PhysX
GTS250 1024 MB

Asus P6T SE (MSI X58 is end   of life)
Tower Lancool K58
750 W Power Supply Corsairs   TX
SSD 40 GB Corsair (OCZ is end   of life)

I know that you have to have matched cards for SLI… I don’t, however, know if you can have extra unmatched cards for computational purposes.

Hybrid SLI only works with Cards of the same architecture.

GTS250 -> G92b GPU
GTX460 -> GF104 GPU

So SLI does not work.

However for CUDA/OpenCL it works, you can put as many cards as you like - at least thats the way it should be.
For PhysX there are restrictions driverwise though. The nvidia driver forces you to choose the card PhysX will run on.

For Octane, best ask in the Octane forum, its a nice and lifely place =) but it should run on multiple GPUs.

PS.: ditch the CM-V8 its not good. I recommend a Noctua NH-D14 and if that´s too expensive, a Scythe Mugen 2 - both got ways better cooling with a lot less noise. Especially if you plan to OC the V8 is a no go.

PPS.: I ran SLI - not worth it at all - waste of money and energy. Best part was when I found out with SLI activated you can only have 1 active screen, and turning SLI on and off requires a reboot. But I read they fixed that annoyance.

Octane will be able to use them both just fine. The only issue is you will be limited to the lesser amount of memory of the two cards (of course you can always switch to only use one card when needed).