I have a Radeon HD4870-based Sapphire card in my desktop PC (Windows 7 64bit) that started getting pretty noisy recently. The temperature reported in Catalyst was hanging around 80C and the fan would alternate between 43 and 46% when idle at desktop. I decided to take the card apart to vacuum out the dust from the fan and heatsink, and to reapply thermal paste.
After that, the average temperature dropped to around 70 when idle, and the fan works around 24%. But it still keeps jumping to 29% all the time and it's not as much the noise level, as the unevenness that is annoying. I installed GPU-Z and this is what I saw:
As you can see, the fan speed keeps changing at irregular intervals. What makes me wonder is the constant alternating of the GPU clock between 500 and 750Mhz when the machine is idle.
There was a bug in this card that made the GPU switch clock speeds very quickly in high performance mode which caused it to crash when playing games etc. I applied the bios update for that and the issue was resolved. Not sure if this is related.
Can I do anything to stabilize the clock rate and (hopefully, as a consequence) the fan speed?