Just slightly off topic but what settings - if i may ask 
- are you using for the Sapphire 7950s? The one in my rig is running at an avg of 603 kh/s, getting it to 630 would be nice. Currently I am using cgminer with
shaders = 1792
intensity = 20
engine = 1075
memory = 1500
w = 256
thread-concurrency = 25088
lookup-gap = 2
threads = 1
auto-fan
and nothing else. I experimented for a day or two with all sorts of settings but this was the fastest I could come up with. Have I missed something or is it just my card? The model I am using is
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202026
EDIT
Just found a tip somewhere else on the forums here - enabling powetune +20 effectively turns it off and stops the cards from trying to save power. it increased my hashrate from 603 kh/s to an avg of around 635 kh/s - thanks roy7 for that tip.
- are you using for the Sapphire 7950s? The one in my rig is running at an avg of 603 kh/s, getting it to 630 would be nice. Currently I am using cgminer withshaders = 1792
intensity = 20
engine = 1075
memory = 1500
w = 256
thread-concurrency = 25088
lookup-gap = 2
threads = 1
auto-fan
and nothing else. I experimented for a day or two with all sorts of settings but this was the fastest I could come up with. Have I missed something or is it just my card? The model I am using is
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202026
EDIT
Just found a tip somewhere else on the forums here - enabling powetune +20 effectively turns it off and stops the cards from trying to save power. it increased my hashrate from 603 kh/s to an avg of around 635 kh/s - thanks roy7 for that tip.
Can you share your powertune resource?
I was getting 635khs with:
intensity = 20
engine = 1075
memory = 1500 (looks like we both found the magic numbers for these cards)
w = 256
thread-concurrency = 21712
vectors = 1
threads = 1
auto-fan
1.25v
in GUIminer using cgminer
lopheaded, eroxors -- I'm in progress testing, will update after I have some data
I'm using cgminer directly on a headless machine running xubuntu 12 with catalyst 13.3 drivers. You can try adding the --gpu-powertune 20 to the cgminer parameters but it seems like GUIMiner is already doing this since you're hitting 635 and if you\re using GUIMiner I'm assuming you have a screen connected - which intensity 20 that might be causing the errors. Try using cgminer directly by unplugging the monitor and sshing into the machine and running it. or maybe just run guiminer and unplug the monitor and see if your pool results change