Cycles SSS on Multiple GPUs

I did a search and didn’t see anyone complaining about this so I thought I would ask. I’m having an issue rendering subsurface scattering with multiple GPUs. When I select one, I have no issues but when I select both under Compute Device, it bogs down and takes 100x longer to render. Anyone experiencing this?

I’m in “Experimental” Feature Set of course and I’ve tried on a simple test scene with just a cube and get the same result. I’m using 2 gtx780s with 3 gigs per card.

Hmm… I disabled SLI and it’s rendering fine now. 1:18 on a single 780 went down to 0:42 with the two GPUs in contrast to 2:54 on the CPU, so it’s definitely worth it.

SLI is a known speed killer when using GPUs as compute devices.