Need help troubleshooting black screen following unstable overclock on Radeon HD 7850

Hello all,

So recently I upgraded my ATI Radeon HD 4890 for an ATI Radeon HD 7850 (brand: XFX). Everything runs golden on stock settings. As I usually do, I decided to try out the overclocking as I heard that the HD7850 is a good overclocker. I pushed from stock core clock 860 MHz to 1050 and was stable without changing voltage - any more and that was black screen or vertical lines crashing. So then I saw about upping the voltage from stock 1.138V to 1.225V, and I found I could up the core clock to 1175 MHz and be stable (with +20% power draw). Meanwhile, I found a cozy home for the memory clock at 1350x4MHz and left it at that. I could run Bioshock Infinite and Diablo III for extended periods of time with no problem. Good stuff.

Yesterday, however, after playing Diablo III for an intermediate period of time, I ran into a straight black screen crash - with the power still "on" as far as I could tell. Had to hard reboot. Now, what's odd is that I was relatively certain that my overclock was stable; temps never rose above 76ºC in normal usage, and in fact when I pulled back the memory clock the temps were usually around 72ºC (and even lower - talking 68ºC - for less demanding applications). While not optimal I considered this acceptable. So I loaded up HWinfo and went for it again - another crash occurred and I rebooted and checked the data spreadsheet. No odd behavior whatsoever except for the crash.

I dial back the overclock to 1100 MHz on the core clock and 1300 MHz on the memory clock, and eventually I got another crash. So I reduced the voltage to 1.138V and dialed back the overclock to stock settings (with normal power draw) - I also confirmed that it was back to stock with GPU-z. I uninstalled all drivers/extra clocking programs and reinstalled latest drivers from ATI. Still more black screens - although fewer and further in between. In fact, I can only achieve stability when I underclock the GPU to 800 MHz on the core clock and 1100 MHz on the memory clock. With these settings, there are no more black screens.

So. I need help troubleshooting the culprit. The GPU is likely because I did give it a pretty demanding experience with the benchmarking, and maybe I even overdid it on the overclock. Oh well. But I also have the feeling that it could be my PSU since the GPU seems perfectly stable when underclocked - maybe I was asking too much of my PSU after all, and it just couldn't handle it?

Hard to say. Here are my specs:

AMD Phenom II X4 965 - 3.4 GHz Quad-Core (NOT overclocked)
ATI Radeon HD7850 XFX Double D
PSU: 530W Rosewill with 20A/+12V
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More about troubleshooting black screen unstable overclock radeon 7850
  1. Not sure. I OC my 7850, but the highest I could get without your black screens was 1050 core and 1350 memory. It's completely stable now. Anything higher it just crashes. Perhaps it could be your psu, there are ways of testing that.
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