If you're using the newest cgminer or sgminer, try these settings. They seem to work quite well for two of my Gigabyte 280x's. 717Kh/s at 709wu each.
-g 2
-w 256
--lookup-gap 2
--xintensity 768 (xintensity has turned out to be exactly what I needed to do minute adjustments to get all my cards working very well with this pool!)
--thread-concurrency 20480 (using the 20480 Lantis bin that comes with the new sgminer)
--gpu-engine 1055
--gpu-memclock 1500
--gpu-powertune 20
--auto-fan
--gpu-fan 30-85 (I had to set this a few months back because one card kept staying so cool, the fans would turn off and the card would go sick. This forces that card to always have the fans at least at 30% speed)
--temp-target 76
--gpu-vddc 1.025 (yes, undervolted to 1.025 and running smoothly)
Both cards are currently averaging about 5% rejects with those settings. I'll even link ya to the sgminer thread in case anyone hasn't heard of this wonderful version of cgminer yet.
http://coinmyne.proboards.com/thread/24/sgminer-compiled-version-downloadCan anyone direct me to a place where I can ask some config questions? I got some 280x's in and up and running using the settings I have seen posted around but I am not getting anywhere near the hash rate that they are claiming. I'm not sure if that is because I use GUIMiner-scrypt and Afterburner or not. I have yet to figure out how to successfully set up CGminer with more than 1 gpu.
I would post it here but I don't think that this is the forum for it. Thanks!
Thanks for the help! I'll mess with these tonight once I get home. Got both cards up to 720 using Thread concurrency-11200, workersize 256, gpu threads-2, vectors-1, and intensity-1. Clocked cards to 1050 core clock and 1500 mem clock with 20+ Power tune. They are stable and have been running that way for about 3 hours now. I'll try your settings once I get CGMiner set up.