I have tested all kinds of configurations and finally the highest hashrate I can get out of my 7950 cards (with stability) is 630 KH/s. I have seen people reporting hashrates of over 700KH but I just can't imagine how to get there at this point.
Currently the cards are configured as follows:
Intensity: 20
Powertune: 18
Memory freq: 1575
Engine freq: 1110
VDDC: 1.1 V
With these parameters I have the cards running stable at around 72°C. If I increase the engine frequency I might get a few more KH (not so many) but eventually the whole system hangs up or one of the cards appears as "DEAD" on cgminer. I have also tested a very wide range of different frequencies for memory and GPU engine but this is the best hashrate I have achieved.
I'm curious to see what does your .bat file look like? Thread concurrency specified and other settings?
It looks like this:
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU-USE_SYNC_OBJECTS 1
cgminer --scrypt -o stratum+tcp://middlecoin.com:3333 -u XXX -p x -I 20 --gpu-engine 1110 --gpu-memclock 1575 --gpu-powertune 18 -w 256 -g 1 --lookup-gap 2 --thread-concurrency 24000
Generally I also end up setting the fans to a fixed speed (75% to 85% depending on the weather) so the temp is stable