From Reg Hardware:

Can a budget graphics card really be this fast?

The RV740 graphics chip at the heart of AMD’s new budget Radeon HD, the 4770, is an interesting wee beastie. It’s wee because this is the first graphics chip to use a 40nm fabrication process rather than the 55nm process used in HD 48x0 series and in Nvidia’s latest GeForce GTX 2xx chips.

Alright, this guide is for those who would like to vmod their graphics cards/mobos but don't know where to begin. This method works in most cases, but sometimes there are obstacles like overvolt protection etc... so try it at your own risk. This mod will void your warranty.

The rest can be found in the forum here.

Over-clockers are always looking for a way to squeeze every last drop of performance out of their hardware.  This has been going on for years. Today’s Video Cards are great candidates for over-clocking.  Many have high-end capabilities just waiting to be released.

As any over-clocker knows, an increase in voltage can sometimes net a moderate to great increase in the overall over-clock, but there is no guarantee that this mod will offer any increase in your over-clock.  With that in mind, we will be showing you how to perform a BIOS volt mod to your 6  or 7 series card.