7870 Overclock

Hardware Overclocking
1

Hey guys,

I have a question regarding overclocking my asus directcu II TOP 7870. I am using GPU Tweak which is just the software that asus provides for overclocking. I was able to get a stable overclock at 1300 mHz core, 1375 mHz memory and voltage at 1300 (up from 1219) after running the 15 minute FurMark burn in test at 1080p.

After running this test twice I decided to run the synthetic benchmark that is included with Hitman Absolution just to test performance increases. About halfway through the test my PC just turned off. I really doubt it had anything to do with temps because throughout the whole FurMark test it was running no higher than 65 C. Also, I have a 750W psu so I wouldn't think power draw is a problem.

Any ideas or suggestions are welcome. Thanks in advance.

2

what IS the psu?

generally it's a psu overheating that will cause that type of shutdown without a blue screen.  Usually you'll get a warning, a beep or something if it's a cpu or gpu overheating... graphical corruption or something.  PSUs however will just shut the system down.  If you've got some junky 750W psu it might not "really" be a 750W psu... and after prolonged use at moderately high energy draws it overheated and shut down.

I've seen some cheap PSUs claiming 1000W when tested could only push out 300-400W of energy before failure.

3

Its a 80 plus bronze rated AX750 from Corsair so its pretty reliable when it comes to power. As far as the process it goes through to acutally shut down the computer it usually just goes to a red screen directly from the benchmark and then the PC resets itself. I don't know if this would have anything to do with that but I am using Windows 8 as my OS

Thanks for pointing out that I didn't actually say what the PSU was and thanks for the quick reply. I had heard that shutting down meant the PSU was overheating but I thought that the 750W was more than enough power for the system.

4

First of all, you should not be testing with Furmark, avoid it like the plague.

 

Test with Unigine Heaven for stability, and maybe a shot of 3D Mark Vantage.

If it crashes with no BSOD, that would be your GPU cutting out, this happens when they get too hot, and throttle.

Use a better overclocking tool, download Sapphire TRIXX (works on all brands of Radeon cards).

5

And before you think it is not a heat issue, all GPU's have VRM's, it matters very little if your GPU core is cool, but these are blisteringly hot....

 

6

I ended up getting a stable overclock at 1200 core 1300 memory and 1238 voltage. But I encountered another problem. I had been playing Crysis two for about 2 and a half hours and was just getting to the end of the game when my fps plummeted. Of course I stopped the game and looked to see what was wrong and it seems that my clock speed had dropped down to 150 mHz and wouldn't come back up (memory also went wayyyy down). I had been checking the temps the whole time while playing but as you said the VRMs could be hot so I don't know. I did restart my PC and the everything was working normally again.

7

Oh, and even though I got it to a seemingly stable overclock I downloaded Unigine Heaven and will be running some of the stress test that it provides.