Hi,
I have powercolor hd5850 pcs+, and I have tried adjusting the voltage of the bios I saved using gpu-z, this is the same bios in the techpowerup vga-bios collection marked 2010-01-18 23:39:00 as the date compiled.
In the clock-/voltage settings table, I changed 1.038 to 1.25 @ 760/1050...