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I bought two 7950 Sapphire 3Ls at the beginning of April. I run them both at a modest overclock, which gets about 590 kh each, and temps have always been around 65C on one and about 55 on the other. The one at 65C is the card running good results as i type this, the one at 55C is poorly producing.

Anyways, i noticed earlier today in GUIminer that my hashes for one card were WAY lower than the other. (about 1/5 as many) So I closed and reopened GUIMiner. Same thing. I shut the PC down let it rest for a few minutes, and started again. A few minutes later the card in question has Accepted 34 shares, stales 4. The other card (which was started at the exact same time) has 193 accepts and 3 stales.

The poor results card is still getting the same 590k/h it always has. Is there anything I can do to try and fix things? What do you think is going on with the card?

see if the rate falls after a few days. it it declines, rma the card.

Maybe a driver issue...might need different version or reinstall.   Could also be temp related.  Card being throttled?

I'd give cgminer a try. It's not that hard to use, and you get a lot more controll over your cards. I used guiminer for about a day, and gave cgminer a shot. I'm not going back. I've been mining on 4 7950's for less than a week. Have about .5 btc in profit. Not as much as I though I'd make... I need to hook my other 2 new 7950's up, but don't have any room in the computers case. Maybe I'll get a riser?

GUIMiner doesn't give you the tools necessary to make any kind of diagnostic. As mentioned, give cgminer a whirl, you might be getting HW errors, which I assume is the case, as 590KH/sec is pretty high for a 7950.

Have you tried to move the card? Switch slots with the other card and see if your hashs change or stay the same for each card. If they stay the same then its likely a gpu issue. If the hashs change(new card in old slot gets low hashs now) then its probably a issue with a driver or the mining software. Cgminer is really nice.

Alright buddy, what is the exact model of your card?

You should be able to get 700Kh/s+ on scrypt mining with a 7970.

I have two sapphire 7970's vapor-x ghx edition and was only getting 550Kh/s untill i did a simple BIOS flash. Now i get 730Kh/s with voltage and core speed underclocked, running at 60C.

I wrote a thread yesterday with what to do, check it out - https://bitcointalk.org/index.php?topic=200777.0

Hope this helps :)

Edit - I'm an idiot, i thought you said 7970 :P

Still though, you should be able to get more than 550Kh/s and if i remember correctly a guy i helped the other day had a 7950 which i think he said he got up to 650Kh/s.

One of my 7970s is running up into the 95C range while the others are in the 80s. Any explanation for why this could happen?

It's summer time for one, and also these cards seem to naturally run very hot. 60s isn't running hot.

What model do you have?

What are the voltages?

The sapphire vapor-x ghx comes at 1.256V which is way way more than you need. With a simple undervoltage temps go right down.

Is your second card directly next to the 1st card? If so, then it will rub hotter due to restricted airflow.

My first card runs 60C @ 50% fans, the second runs 70C at 70% fans, but i have a PCI-e riser in the mail to fix that.

It's three cards in a row. It seems to be getting good airflow as the whole room heats up from it.

What should I undervolt it to? What is a good level? I will have to give that a try today.

I'm using SAPPHIRE 100352-4L Radeon HD 7950 3GB GDDR5 PCI-Express Video Card x3 and it's overheating to the point of shutting down. So I reversed the overclock and still it's doing it. I'll keep tweaking.