This thread could serve for HD4850 BIOS editing discussion.
I have seen two bioses so far, one is version 011.004.000000 (6 zeroes omitted on purpose) and the other is 011.003.029117.

In 011.004 clocks are at offset 0000ACD0 starting with two last bytes for core clock.
I am particularly interested if anyone has modded his bios with clocks higher than Catalyst Overdrive allows, and if anyone has newer bios than 011.004.