Changing core voltage on a 5850?

[aaa801]

i have a Sapphire Radeon HD 5850 Vapour-x Graphics card
trying to overclock it to get more mhashs but aparantly it doesnt support voltage changing :/
is there a workaround for this

[scintill]

I can change my 5850's voltage and clocks with atitweak in Linux.

Edit: Sapphire HD 5850 Xtreme 1GB

[drakahn]

if its anything like my 5830 its locked in the hardware

you can do a pencil mod to get around it, but i haven't done anything like that nor have the right tools, so yeah. google gpu pencil mod