Overclocking HD5850

[LiveFreeOrLagHard]

Hello,

I've got a couple year old HD5850 and since the warranty is now void I decided to overclock it (I should have done it before now, but well).

The problem is, if I use the AMD overdrive software with the latest version of CCC, and put it to anything but the stock speeds, it starts to freak out.

When the GPU is virtually inactive (Just browsing the web or something alike), I mostly drops the GPU clock to about 400MHz, which is fair enough for me. When I overclock it however (Even the slightest bit), it runs without any problems in games and benchmarks, but it drops the GPU clock ridiculously low when inactive. As low as 75Mhz. This will cause any window I have open or am scrolling through to freak out, the GPU activity randomly peaks to 80% and AMD overdrive throws the clock up to whatever I overclocked it to. After this everything will run smooth on my overclock settings for about 10 seconds and it drops it down to 75MHz again.

The moment I reset the initlial values it runs normally again. It does this at all temperatures and with any deviation from the stock clocks. This has nothing to do with me overclocking it too far (which isn't even really possible with the AMD software), it does it even 1Mhz above the default 726.

I can probably set it to run at high performace settings all the time but I don't think my power bill is really going to like this. Does anyone know a good way to slightly overclock this card? (preferably without having to flash the BIOS, it's a Sapphire one).

Thanks in advance!

~LiveFreeOrLagHard

[Helltech]

Use Afterburner instead of CCC.

[Dai909]

You could also try Sapphire Trixx to overclock as well. I have a pair of 5850's in crossfire. My primary is a Sapphire 2gb Toxic and second card is a 1gb Powercolor 5850.

I went down the bios flashing route to overclock both cards. I used the Radeon Bios Editor (RBE) to flash both cards to 5870 spec clock speeds. It also gave me greater room to overclock. It's very easy to use as you can flash the card in windows. Just be sure to have a standby card in case you brick the card with a dodgy flash.

Both cards are OC to 850MHz on the core and 1150Mhz on the memory. Unfortunately because both cards are non reference in design voltages are somewhat locked. But with the bios flash I able to raise them 1.150v. Both cards are cooled with Arctic Cooling Twin Turbo Pro coolers with Arctic Silver 5 thermal compound. Temps according to GPU-Z are 38-40 degrees Celsius for primary and 28 for the second card.

3dmark Vantage benchmark score using the latest beta drivers from AMD (13.2 beta 5) is 26787 in the performance test.