4850 won't overclock

[mame]

Had my 4850 for about a month and decided to try a bit of overclocking. If i set the core or memory even slightly higher 650(626) and 1000(993) i get bad stuttering. I've only tested this on 3dmark06 which i know isn't the be-all and end-all but it's enough to tell me something isn't right.

I thought it might be the PSU which is an antec truepower 480w but, giving it some thought, it would seem lucky that it has just enough power to run it at standard clocks (never had 1 single crash). I then thought it might be temperature related but the stuttering happens straight away. At the default clocks i can game for hours with no problems.

I've tried upping the pci-e voltage 0.1v and ive tried increasing the pci-e bus the 105. It's the same with th 8.6 hotfix and the 8.7s

Any suggestions ?

EDIT: I've just tried the devil may cry 4 benchmark and it's the same. Stutters every 3-4 seconds as soon as it starts running

 

[Helios1234]

I found that slight overclocking on my friend's 4850 caused really bad artifacting on atitool. Maybe the fan fix could help:

http://forums.overclockers.co.uk/showthread.php?t=17898680&highlight=fan+control+4850

http://forums.overclockers.co.uk/showthread.php?t=17908743&highlight=fan+control+4850

 

[mame]

Thanks. Tried that but it doesnt solve the problem. the idle temps drop about 25c though!

 

[gareth170]

not all cards get the same overclock results. its just the same as cpu's.

my card can only do 680/1030 without getting problems.

 

[Xiler]

have u left in running to see if it keeps stuttering?

some games stutter just as they load up for a few secs.

have you tried overclocking just the core? i know my bros 4850 memory doesnt clock that well but can run the core at 700.