Gigabyte HD 7850 OC TwinForce 2x graphics card is a factory overclocked card, whose GPU was boosted by 115MHz but the memory left at reference 1200MHz (4800MHz GDDR5). We managed to overclock the GPU higher, to 1025MHz.
We expected a better overclock since the cooler does its job great. GPU temperatures didn’t exceed 56°C at factory clocks, while our overclocking increased them by a single degree Celsius. We left the fan in AUTO mode durin our overclocking because thermals were good and the fan quiet. Increasing the RPM manually didn’t provide for a better overclocking score. 
We left the memory at 1200MHz because even the slightest boost of 50MHz caused our system to freeze. In fact, not even a system restart managed to help on few occasions, and we had to resort to throwing in another card and clearing the drivers.
As far as noise goes, fans are inaudible. We didn’t hear them until they exceeded 70%RPM (which was never the case in AUTO mode). When the fans exceed 70%RPM, you’ll hear a very faint buzzing noise. We’re not sure what’s the cause, but it’s most likely the fan vibration causing parts of the heatsink to vibrate as well. Note however that it’s far from loud – in fact, you won’t hear it away from the computer and pretty much never in AUTO fan mode. 
