hmmmm... after searching from a long time i hav finally overclocked my sapphire ati radeon 4770.. from its default gpu clock of 750mhz to 1000mhz and its default memory clock from 799mhz to 1200mhz..
but it required more cooling at this clocks...
u cant overclock more than 830/850 with its default bios coz it doesn't support voltage more than 0.9v..
so hr is all u need for overclocking ur graphic card
asus top 4770 bios coz it supports voltage upto 1.3v..
u can download it from here...
http://www.techpowerup.com/vgabios/46159/Asus.HD4770.512.090414.bin
after this, u need to download atiflash ( i hav done it with version 3.60 )
u can download it from here...
http://www.techpowerup.com/downloads/Utilities/BIOS_Flashing/ATI/
thats it now prepare ur system..
first u need a dos boot disk..
now locate atiflash dir and enter it
now type atiflash -f -p 0 4770.bin ( dont try to run t from windows and remeber ur bios file name may be differ)
here -f is to force the program to write bios with checking subsystemid's, -p is the adapter choice for pci-16x adapter, 0 is the adapter number, and 4770.bin is the bios file name.......
thats it......
m surprised ...