Hi, I have Sapphire 7950s. From what I read they supposed to give 640Kh/s at around 72 degrees and most of the ppl like them. I can barely scrape 500 KH/s out of them and need to overclock to even get there. I have 2 presently connected to 1000W supply and the other 2 to a 1350W supply. Both PSUs are gold series. I tried to put them on raisers - its even harder to get the Kh/s then, tried to blow additional air through, but they just dont want to cooperate.

I have these cards:

http://www.newegg.com/Product/Product.aspx?Item=N82E16814202026 - these are the worst, should I flash them? They are v locked and I can't undervolt them.

http://www.newegg.com/Product/Product.aspx?Item=N82E16814202030 - these are a bit better. When I run a single card I can get a good 550 Kh/s with fan at around 65% sits around 72 degrees. But I can't get 600+. These can undervolt but that doesn't do much.

I am listing AVERAGE Kh/s value, the one that shows in cgminer on top left after the 'per second' value.. I hope thats the one everybody goes by.

The best setting I found is:

1100 core, 1250 mem at 1200v core.

Should I ROM flash all these 7950s or something?

I have read a bunch of different settings but nothing works for me...  .

I use these components:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820239312
http://www.newegg.com/Product/Product.aspx?Item=N82E16817194105
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139057
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128627
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103888

Please advise how do I improve the hashes and decrease the heat.