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First time OC with Sapphire 7950 - increasing memory clock decreases performance? - Page 2

post #11 of 15
not really what you were asking about, but might have some useful info on the 7950's
http://www.overclock.net/t/1203636/official-amd-ati-gpu-mod-club-aka-the-red-mod
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post #12 of 15
Thread Starter 
Okay, so something really bad just happened. I loaded a Youtube video and my screen went all glitchy, couldn't do anything so I had to reboot. Tried it a couple more times, same thing happened. Opened up GPU-Z and found my voltage sitting on 1.169 at idle, even though at full load the highest it had gone previously was 1.13. Tried scaling back the memory clock in CCC, it stays at 1.169V all the way down from 1500 to 1255, but when I go back to the default of 1250 the voltage reverts to 0.944. With the voltage at this level I don't have any problems with Youtube.

In summary, even though it handled a big memory overclock with no voltage change before, it changed all of a sudden and now boosts the voltage for anything even slightly over default, which causes my screen to freak out. No idea why it's doing this as it was fine earlier in the day. Any ideas?
post #13 of 15
That's normal for that voltage. IMO you should bring the voltage up to 1.25v and memory up to 1.55v and rock out an OC of 1200/1600. Just use GPUz to watch your core and VRM temps. My Sapphire can only go up to 1165 core. My MSI TFIII can go up to 1250. Its all luck. What drivers are you using? Btw you might have to lower your OC a little once you start playing games. In all reality games are the best test for stability.
post #14 of 15
its normal
my card is the same way, just bump up the core clocks and call it a day.
post #15 of 15
Thread Starter 
I was using the 13.4 drivers, I tried upgrading to the 13.6 beta to see if that helped but it's the same.

I don't understand how this is normal if it was working very differently before. It idled at 0.944V with the memory at 1500, and got to 1.13 under full load. All of a sudden it now idles at 1.169 at anything over 1250, even 1255, despite no voltage manipulation on my part. It just doesn't make sense to me. I'm completely guessing here, but it seemed to start happening once I started trying to unlock the voltage in Afterburner (which didn't work in the end). I've completely uninstalled the app and it's still happening, so that's probably just a coincidence. I don't really want to toy around with the voltage for a while, maybe a year down the track or so.

I'll probably stick with my 1100/1250 overclock for now, but I'm still wondering why it worked perfectly at 1100/1500 for a while and now even 1100/1255 breaks everything.
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