the card runs in 2D mode it is very silent and you wont be able to hear it. Also
compared to a GeForce 285GTX or a ATI Radeon HD4890 the 5870 is much more quiet.
Also in 3D mode the cards noise level still is on a very reasonable level and
this let's us think that it might be an interesting object to be overclocked.
Using the delivered software SmartDoctor you can raise the core voltage slightly
and achieve quite astonishing clock rates. Generally we can claim that a higher
core voltage (max. increase ten percent) results in better overclockability.
To the comments