So far I'm doing 905MHz core, 1100MHz memory on a HD4850 with 1.55vgpu under an Arctic Cooling S1 with a ~110cfm fan strapped to the heatsink. No heatsinks on the pwm, chokes, or memory modules. Suspect once I sink the mosfets and chokes and put this under dry ice that 1.55vgpu will yield 980-1000MHz. Mosfets get pretty hot, around 65C according to my k-type probe.