Sapphire HD5850 toxic 1gb OC problem

Hi
I tried to overclock my sapphire hd5850 toxic 1gb gpu, but can only get it to 860/1200, when it become higher than this value, will fail in furmark and starcraft 2. But I saw a lot of ppl oc 5850 toxic to more than 900/1200 and can still run it 24/7.

Is this the problem of my gpu or I should try some other way to oc it?

PS: temperature is not a problem, load temp is around 65.

You'll need to bump up your voltage!
Instability, I believe, is just when you don't have enough voltage.

Make sure the temps are really as low as the software's saying. If the heatsink feels to hot to touch even for a second then there might be something wrong.

tinymouse2 said:

You'll need to bump up your voltage!
Instability, I believe, is just when you don't have enough voltage.

Make sure the temps are really as low as the software's saying. If the heatsink feels to hot to touch even for a second then there might be something wrong.

Click to expand...

But this card is voltage locked, cannot change at all. >(

Really? Even if you flash the BIOS? I've never changed the voltage on a GPU before so I don't really know what I'm talking about but I know you need to change it and that it might be possible in the BIOS.