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.
Keep in mind the single biggest mistake people make is thinking that hash rate is the only part of tuning. Efficiency or WU is the real number to be concerned with. You would much rather have a card pushing 630 k/hs withWU of 600 (95.23% efficiency) than that same card cranked up to 700 khs and a WU of 500 (71.42% efficiency). At really high hash rate a majority of cards unless expertly tuned are simply just spewing garbage hashes that cannot be used.
I highly suggest you read all of the "Read Me" in the cgminer folder. They are very informative about this subject.
Best of luck,
~BCX~
Yes that's completely true. I have a pretty good ratio IMO (average WU around 580 and no HW errors). I will have a deeper look at the readme, thanks for the tip!