Why cant I overclock my 4870X2?

[danielanthony]

Hello,

I've got my 4870X2 water cooled, so it idles at 39oc on both GPU's. I have enabled ATI overdrive through CCC and pumped the GPU to 800Mhz and memory to 1000Mhz - it also puts these settings if I allow it to auto tune.

But, when playing a game, there are loads of artefacts, so I have to reduce the speeds back down to defaults to display the game normally again.

So what am I doing wrong? My temps are low enough that I should get to 800Mhz surely?

Thanks,

Dan

 

[Sash]

Have you tried at a smaller overclock first? Dont try to jump for 800/1000 straight away. Install 3dmark06, open up your overclocking program, increase the clock by a small amount then run 3dmark06, repeat and stop when things get artifacty.

 

[Wizardskills]

There may not be enough voltage going into the GPU cores for you to get that overclock. That is prob why you are getting artifacts. Either that or you have the mem overclocked to much. Try setting the mem to its default speed and increase the core speed by 5 Mhz increments and testing it each time.

 

[reflux]

From my experience, the higher end ATi parts tend to be clocked within an inch of their life on their default voltage supply, so overvolts are needed for anything more than very small overclocks.

 

[danielanthony]

Fair enough, but a 50Mhz increase is only 6.5% over stock, surely these GPU's can handle more than that?

 

[danielanthony]

Ok, more volts might be needed!

 

[arc@css]

Wasn't there a post recently about the Gainward factory overclocked versions being slower and more unstable at overclock speeds. Mine (HIS) seems to be fine if I push it to 800 / 1000. Haven't tried 3rd party software though my 512 4870 doesn't overclock well. It'll select, in auto tune, around 825 - 845 (factory o/c version) and 1090 memory but during games it, like the OP said, it lets you know it isn't happy.