Originally Posted by Terrere
Thanks! I'll up the voltage then to 1.45 and see if I can survive the blend.
I am definitely planning on overclocking the GPU after my CPU. I've downloaded Trixx, Unigine Heaven, 3DMark11, and Cinebench. Do you suggest these (or possibly others) for testing GPU stability? I ran 3DMark and Unigine when I first built the rig.
I don't use Cinebench personally.
Avoid Furmark. It runs MUCH hotter than other GPU benches and can quite literally blow up your card (seriously- I've heard of people doing high overclocks and running Furmark for 24 hours and blowing their cards VRMs).
3dmark11 and Heaven are both great, but the cutting edge now is the new 3dmark with Fire Strike and Unigine Valley. Fire Strike is okay- Valley is probably better since you can have it loop after you benchmark. I would highly suggest getting Valley.
Other than that, one of the best ways to test is real world usage in an actual DX11 game. Get something like Crysis 3 and actually play it and watch for artifacts. Run in Windowed mode and use the Trixx sidebar gadget to monitor things like temps and fan speed as you play. If you aren't into Crysis then just use whatever modern games you have lying around and play them for a few hours. Use Valley to bench and test your initial OC. I don't know much about the 7870XT but if you have good cooling you should be okay putting up to 1.3v through it to overclock.
I looked up your cards GPU-Z and it says stock it's 975/1500mhz. Almost all of the performance gains with AMD cards come from upping the core clock. You can either leave RAM alone or try setting it to 1600mhz. You might want to look up the 7870XT owner's club here and do some research into what kind of stable overclocks people are getting with your card. I know 7970s and 7950s can do 1150mhz core easily. Good chips can do 1200mhz. Golden chips do 1250mhz or even 1300mhz commonly but this is rare and requires water cooling to cool. Since the 7870XT is also a Tahiti core, you can probably expect to get at least 1100mhz on the core. Depending on heat and whether or not you're artifacting in the games you want to play, you may be able to get more than that.
Watch your temps. Anything over 70C is dangerous, but again this depends on the card and other factors, you may be able to pass 70C and still not artifact. I have the Sapphire 7970 Vapor-X and I paid $450 for it in April before the price went down. One of the fans on the cooler stopped working after a month and my temps went up with the same overclock (1200/1600). Temps used to stay at 62C in Crysis 3 and the game ran fine. With the broken fan the temps would eventually go to 70C and the game would glitch out and artifact, and eventually my display driver would crash. Card was not usable for modern games for 2 months, but I didn't realize the fan was broken until recently. So, I got an Arctic Accelero Xtreme 7970 cooler, I couldn't RMA my card, and I couldn't send it to Sapphire because I had replaced the thermal paste to try and fix the temp issue, and it was obviously tampered with (which voids the warranty). Anyway, it worked out in the end because the Accelero Xtreme cools better than the Vapor-X cooler. I only hit 58C in Crysis 3 now, and it's MUCH quieter. I don't think you need an aftermarket cooler or anything, just relating my experience. This is why you should try not to let your card pass 70C.