I've got two SLI-enabled GTX570 cards (drv. 296.10), 16GB RAM, Intel X79 Express chipset on Win7 x64, BOINC 7.0.22 x64. Until recently, everything with GPUGRID was okay, but after one of the late updates of acemd with long tasks (currently the executable is named acemd.win.2352 - crunches NATHAN FAX4, CB1), the following problem appeared:

Everytime two GPUgrid tasks are executed at the exact same time (eg. BOINC launch / excluded application closes), the two tasks get assigned to the same GPU , but it is a real pain: GPU usage of both is ~35%, but the system reacts really sluggish - mouse moves in 3 sec. intervals and cards are relatively cold. When I suspend a task and another one gets launched instead, it is temporarily fixed - both cards get used up to the limit of specific WU, about 90% when running NATHAN tasks.

I believe this is a problem in acemd code, because multiple Seti@home GPU tasks work just fine. Moreover even if I exclude only one GPU from running GPUGRID, it works fine as well.

Yes, SLI is enabled for the sake of games in control panel.
I tried to create a profile for acemd executable to run Single-gpu, but it didn't help. Even with current settings, a task always uses only one of GPU (as shown by afterburner, gpu usage). That was valid for seti@home and most gpugrid tasks.

I just found out, that the tasks don't have to be launched at the same time, only problem is when two NATHAN task are running at the same time (FAX* x CB* or FAX* x FAX*). If one task is NATHAN and the other is GIANNI or IBUCH, it works fine.

Well it does make a difference, when I disable SLI globally, it behaves differently than when I disable SLI for acemd (as an exception). The GPU usage is more stable and I believe a bit higher (~5%) than with SLI enabled globally.

Thanks for helping with the solution. I'll keep on looking for a better way anyway, one where I wouldn't have to switch SLI option on and off every day.

Well it does make a difference, when I disable SLI globally, it behaves differently than when I disable SLI for acemd (as an exception). The GPU usage is more stable and I believe a bit higher (~5%) than with SLI enabled globally.

Thanks for helping with the solution. I'll keep on looking for a better way anyway, one where I wouldn't have to switch SLI option on and off every day.

What kind of temperatures do you see on your cards with GPUGrid tasks running? The second GTX 570 caused temps to rise about 16C in one computer. The GPUs report about 80C. Both cards are set to 1.100V and are overclocked to about 920MHz. What temps should cause concern? The max for the GPU is about 96C.

thanks