To raise switching frequencies of chipsets, cooling the semiconductor device is only part of the equation. By raising operating voltage, transistors withstand faster switching during overclocking.

These are the device IDs for each core so you know which "core" you're adjusting when you run the Vgpu modifications.

Switching over to Windows XP and Performance mipmaps, we ended up with 918MHz/1134MHz on the GPU/MEM clocks. This was acheived with 1.49V on BN:4 and 1.43V on BN:3 (all voltages measured in 3D mode). Memory voltage was untouched. GPU quality differs across the board, so expect to treat them like individuals graphics accelerators when voltage tweaking.