Hi,

So here is my problem, I hope someone can help me out.

First of all, my rig is composed of 3 7950s at stock clocks with one 1000w KingWing platinum PSU. One video card hooked up to a display and the 2 others to a dummy plug. It is running on Ubuntu server 12.04, cgminer 3.1.1 with latest AMD drivers.

Everything is running without a glitch except when I go over an intensity of 17, problems start at 18. What happens is the card hooked to the external display runs fine and stable but the two others are throttled: once every approximately 10 seconds, they will drop from 515 kh/s to approx. 420 kh/s for a couple of seconds, and then get back to 515 in this particular exemple. I can easily get a single 7950 to 630 kh/s when overclocked but I am far from getting there with all my cards.

I suppose the problem is not one coming from the PSU since at stock clocks and intensity of 18, the power from the wall reads at max 815 w. I should have enough room.

It is neither a heat problems since the cards at those settings are running at 82 celcius max fans under 4000 rpms.

I thought this could be a driver issue, not letting me use 100% of all GPUs all the time to protect them... dunno. I didn't want to start testing bunch of drivers version since this would be really time consuming. Maybe someone knows of a version working better than others? Tried adjusting --gpu-powertune without much luck, though it seems to help a little bit...

No HW errors, rejected shares of 1 to 1.5%.

Any ideas of what would cause that?

Thanks for your help!

edit: export DISPLAY=:0, export GPU_MAX_ALLOC_PERCENT=100 and export GPU_USE_SYNC_OBJECTS=1 are all set.