The HD4850 is an engineering challenge to cool, with a couple million transistors squashed into an area slightly larger than a dime. Luckily for ATi, the HD3850 was an exercise-in-preparation; pretty much most of the cooling features are ported over.

The single slot thermal solution vents heat towards the rear of the case with the help of a PWM controlled axial cross blower. Flipping over the unit we see that the fan is a 4.8W model.

Active components, with the exception of the GPU, are interfaced via thermal pads. The RV770 die gets a smearin' of grey-goop instead.