To the folks who suggested Kalroth's cgminer with the xintensity feature, you have my thanks. His version is better in pretty much every way, near as I can tell. I have increased hash rates across the board. And I can run my Linux desktop on top of a 7950 doing 600kh/s without it seeming lagged.
Incidentally, I have my 7950's running with xintensity 4, gpu-threads 2, and shaders 1792. 280x's the same except shaders 2048.
Oh, and with this version, I can underclock the memory on my 7950's all the way down to 900Mhz with no change in hash rate, which saves a significant amount of power according to my kill-a-watt. The 280x's wouldn't accept anything but the default memory clock without throwing a fit, however.
Wait a minute, you are getting 600KH on a 7950 @stock? Can you please post all your settings and setup? I am barely getting 550KH @1050/1500. Thanks!
im getting 660kh with this setup
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer --scrypt -w 256 --shaders 0 --intensity 20 -v 1 -g 1 --lookup-gap 2 --thread-concurrency 21712 --gpu-engine 1100 --gpu-memclock 1500 --gpu-memdiff 0 --gpu-powertune 20 --temp-cutoff 90 --auto-fan -o address -u username -p password
I'm using an optimized bin from the first comment on this post and I'm up now to 687 KH/s on my 7950.