4770 overclock more than 872/1000??

You can try increasing the voltage, although what you have is pretty decent already.

The only thing you can do is turn up the fan speed or replace it with a better cooler which probably isn't cost efficient on a non-high end card.
You can't increase the voltage on cards except through hardware modifications usually.

You can increase the volts using software jyjjy.

http://www.techpowerup.com/downloads/1128/AMD_GPU_Clock...

I advise caution while using it. Although nothing seriously bad is likely to go wrong (if you get problems just switch off the pc and it should be fine), use it sensibly.

You can only increase the voltages on certain cards through software and I don't believe the HD4770 is one of them.

Hmm.

This tool doesn't let me change voltages, but I was able to do it using ATI tray tools (I crashed however).

Gonna have to defer to you on that one jyjjy. There is ofc one final alternative, which is downloading the Asus voltage tweak bios but I'm not going there.

I think the safest way to increase voltages is via a soft mod using a DMM. I don't like messing with the bios personally...