"3-way SLI" and "3-way CUDA"

Some mainboard includes 3 PCIEx16 slots. I understand not all of them can do “3-way SLI”.

But if we plug in three GPU of same model to such mainboard, is it guaranteed that all of them can be used as CUDA devices?

Anyone has experience on that?

CUDA can’t use SLI.

If your motherboard is reasonably modern (say within the past 2 years) and it has 3 PCIx16 slots, then it will very likely handle 3 CUDA devices.
3-way SLI is indeed a picky configuration, but CUDA is a lot less particular. You can even mix-and-match the GPUs, I have one system with one 8600GT and one GTX295 (which is two devices) and CUDA sees all three.

Note that you’ll have to DISABLE SLI mode for CUDA to see all the devices though.

That is really good news. In fact, the only reason that I brought these high end GPUs is to play CUDA instead of play games.

To build a system with multiple PCI-E slots on motherboard helps to save overall cost.