i have a 7950 on my desktop, shappire code 11196-19-20g
an old athlon 5200+ 3 gb ram (on board 4 but it read only 3)
win 7 ultimate
i set my cgminer like this:
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer --scrypt -o stratum+tcp://xxxxxxxx -u xxxxxxxxx -p xxxxxxxx -I 16 -g 1 -w 256 --thread-concurrency 18816 --auto-fan --shaders 1792 --gpu-memclock 1500 --gpu-engine 1100 --gpu-powertune -10
normally i start this config, wait 2 or 3 minutes and after i change powertune from -10 to 0
them i climb intensity 17 them 18 to 19 max
i made 618k hash/s and card is very stable, and power consume is 330w all togheter (pc and vga). i calculate only vga need 250/280w, i have a PSU corsair vs650.
hope to this setup help you to improve your hashrate
