Hashrate drops after second card fires up.

[Waramp22]

Windows 7. 7970 +7950
I am running two instances of CGMiner just to keep the settings apart from eachother until things are running stable. Both of the cards are in 16x slots. I fire up the 7970 and it mines as normal, around 640khash/s. I fire up the second instance of cgminer and the first one drops to around 400khash/s. And the second instance of cgminer with the 7950 is nothing special either.

Is this a driver issue?

Are their some commands in cgminer that can affect all instances?

[eretron]

Did u try to use 1 instance with 2 gpu's?

I've noticed that cgminer scrypt mining is very sensitive if you are doing anything else except mining. For example just lunching google chrome and keeping it open drops hash by 15%.

Try to set high priority to cgminer processes in task manager, did the trick for me 680khs jumped to 730 instantly, though I am using just 1 cgminer instance.

[Waramp22]

7970 Batch File = 640khash/s

setx GPU_MAX_ALLOC_PERCENT 100
cgminer.exe --scrypt -o stratum+tcp://coinotron.com:3334 -u Waramp22.Desktop -p xxxx --device 0 --intensity 13 -g 2 --gpu-fan 65 --thread-concurrency 8192 --gpu-engine 925 --gpu-memclock 1730 --gpu-powertune 20 --no-submit-stale



7950 Batch File = 450khash/s
(Just got the card, havent tuned it much)

setx GPU_MAX_ALLOC_PERCENT 100
cgminer.exe --scrypt -o stratum+tcp://coinotron.com:3334 -u Waramp22.Desktop -p xxxx --device 1 --intensity 18 -g 1 --gpu-fan 65 --thread-concurrency 22400 --gpu-engine 1115 --gpu-memclock 1300 --no-submit-stale


So i attempt this:

setx GPU_MAX_ALLOC_PERCENT 100
cgminer.exe --scrypt -o stratum+tcp://coinotron.com:3334 -u Waramp22.Desktop -p xxxx --intensity 13,18 --thread-concurrency 8192,22400 --gpu-fan 65 --gpu-engine 925,1115 --gpu-memclock 1730,1300 --no-submit-stale --gpu-powertune 20,0

And i get 495 and 450  
Something happens to the 7970 when i run that batch file.

[scifimike12]

7970s need "-g 2" for the maximum hashrate.  You'll need to run two instances of CGMiner with "-d 0" and "-d 1".

[eretron]

btw, which 7970 do u have. I've never heard that 7970 hashrate will benefit from power tune...

[Waramp22]

7970s need "-g 2" for the maximum hashrate.  You'll need to run two instances of CGMiner with "-d 0" and "-d 1".

That was my original reason. I am running it with -G 2 now and its running alright, the 7970 is at 640kh/s and the 7950kh/s is at 470. Just need to do some more work on it. Lots or rejects. 

7970 Powercolor AX7970 3GBD5-2DHV2
7950 MSI Twin Frozr 3GD5/OC

I removed the powertune as well. Doesnt seem to have any effect.

[scifimike12]

Which card is giving you lots of rejects?  If it's the 7950 then try lowering the core clock a bit, like to 1050.  I've found that once you get near 1100MHz is when you need to increase your voltage.

And try different thread concurrencies -- something like 21000 or 24000.  To get the highest hash rate with 7950s you need to increase both the core and memory frequencies.  There isn't a special ratio like with 7970s (0.575757 is what I've found to be the best).