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7950 crossfire overclocking help!

Oblivion

Oblivion

Oblivion

Associate
Joined
8 May 2006
Posts
581
Location
UK
Hi,

I have some MSI Twin Frozr III 7950s in crossfire...

However, even the smallest overclock of say 960mhz (from the 880 standard) causes errors and artifacts in my benching test.

Are there any settings i need to be aware of as i have read in reviews these should go to 1,000mhz easy with no voltage tweak needed.

What am i doing wrong?

Thanks
 
Oblivion said:
However, even the smallest overclock of say 960mhz (from the 880 standard) causes errors and artifacts in my benching test.
Click to expand...

Hi.

A nearly 10% overclock is hardly "even the smallest overclock".

Increase the power control sliders in the CCC to +20% so that the cards can draw enough power.
 
PSU should be plenty.

Try overclocking the GPU's individually.

Perhaps you have one that's better than the other.

Perhaps one or both need a voltage tweak for the sort of overclock you're after.

It is a silicon lottery.
 
Oblivion said:
Hi,

Yeah i did the power slider +20%... its just in reviews they all say 1000 mhz was possible with no voltage...
Click to expand...

Yeh i read that to but couldn't get 1000 on the core. However Im at 950mhz and 1575mhz on the clock running stable. I could try and get more out of the core clock but tbh i don't think i need to.
 
Oblivion said:
Cool, is that just on standard volts? You also in crossfire?
Click to expand...

Im not in crossfire, not yet:p And i don't touch the voltage normally. Have you got good air flow in your case? You need to remember when you have crossfire or SLi your cards will get hotter then just a single card. So you should try and find out how much you can overclock just the one card at stable speeds. Then put your second card in and see what happens.
 
Test results...

Hi,

I have just finished a very long session of testing each card on its own and then in crossfire... The results are confusing:

Bottom card (not in crossfire) - The highest clock reached without errors was, 975 / 1500.

Top card (not in crossfire) - The highest clock reached without errors was, 925 / 1500.

Now when testing in crossfire I basically got errors for anything above the stock 880 / 1250.

So it doesn't make sense to be honest. As you can see there is a bit of a performance difference between the two cards, with the bottom one being better at over clocking. Maybe it's partly due to temps being cooler at the bottom, or maybe it's just a better chip.

All this was done in CCC without touching voltage. Overall temps stayed between 70-80c during all of this.

I didn't really push the memory, once I got to 1500 I was more focused on GPU clock speed.

Tom
 
Have you disabled the ulps (power saving feature) not 100% this is on the 79xx but on the 69xx you should disable this as it puts the bottom card into a powersaving mode and can cause crashes when overclocking
 
BaNksY IV said:
Have you disabled the ulps (power saving feature) not 100% this is on the 79xx but on the 69xx you should disable this as it puts the bottom card into a powersaving mode and can cause crashes when overclocking
Click to expand...

Do you know an easy safe way to do this by any chance?
 
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