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Crossfired 7950 won't go full clock speed

post #1 of 7
Thread Starter 
I've got a pair of watercooled SAPPHIRE FLEX HD 7950 3GB GDDR5 OC with Boost in Crossfire that won't go to full clock speed when I run FurMark 1.10.3 (or any other time for that matter) to benchmark the setup. As I'm running FurMark, I am watching GPU#0 bounce between 500-925Mhz, hanging out mostly around 700Mhz to as low as 300Mhz and GPU#1 do the same but maxing out around 850Mhz. Base clocks for these are 850Mhz with a factory boost speed of 925Mhz. I haven't even bothered to try OCing them yet because of this problem right now, but a single GeForce 675 getting better scores than my Crossfire 7950's is rather annoying.
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post #2 of 7
Could it be the power control settings kicking in? if you put it to 20%, does the problem go away?
post #3 of 7
Thread Starter 
That seems to help, it didn't drop below the 850Mhz baseline and the FurMark score for 1080 was 3685pts @ 61FPS vs 2840pts @ 42FPS. This still seems kinda low to me when a single 7950 (850Mhz gpu/1250Mhz mem) is scoring 2602pts. Shouldn't a Crossfire (dual cards) be closer to double that of a single? This is my first Crossfire setup ever, so I'm still new to it and obviously ignorant biggrin.gif

EDIT - Tried running a mild OC (950/1375), they didn't like it and FurMark scores dropped to about 3560pts @ 59FPS. GPU clock of GPU#0 ranged from 500-950Mhz while GPU#1 stayed 850-950Mhz. Dropping back to 925/1250 raised the final score to 3840pts @ 64FPS. All of this with a +20% power control setting.
Edited by LoneWolf3574 - 12/9/12 at 6:26pm
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post #4 of 7
One question, by any chance do you have vsync enabled? Seems like your fps is just hitting 60... could by why you aren't utilizing your cards as they are forced to only render 60 frames. (Hence the drop in clock and gpu usage)
post #5 of 7
Thread Starter 
I checked the setting in CCC and it's set to "off, unless the application specifies".

I ran it with no OC (925/1250) and got 4067pts @ 67FPS, but with an OC (950/1375) it's getting 3470pts @ 57FPS (each at the same resolution as before 1920x1080). This is confusing and confounding me to no end at this time.
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post #6 of 7
I hope I didn't miss this. But, do you have both clocked the same. I do not believe crossfire syncs the clocks. It could be possible that one of your cards are oced while the other is left at stock and causing problems.
post #7 of 7
Thread Starter 
You bring up a good point, but I hadn't mentioned it before and I'm using TRIXX (by Sapphire) to OC. I make certain that they are clocked the same using a setting in the program (a bit of a OCD thing for me).

EDIT - I don't know if it makes a difference but ULPS is disabled as well.
Edited by LoneWolf3574 - 12/10/12 at 7:00pm
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