Stefan Mileschin

In a busy week that’s going to end up being just a bit busier, AMD has pushed out another Catalyst driver update specifically targeted at the new Radeon R9 290 series, Catalyst 13.11 Beta9.2. This release is especially notable because it resolves some outstanding issues with the hardware that the hardware press has covered in depth this week opposite the 290 launch, and because it is making low level operational changes that will have a direct impact on the power, noise, and performance characteristics of the 290 series.

First off, let’s talk about what AMD has done with their drivers. Citing an issue with variability in the fan speeds on 290 series cards, AMD has changed the algorithms for how their drivers handle the fan speeds on 290 series cards, essentially overriding the BIOS defaults with new values. This is similar to how AMD deployed their specification changes for the 290 ahead of its launch – adjusting it from 40% to 47% as the default maximum fan speed – but AMD has also used their driver update to change how they’re defining and controlling fan speeds.

Rather than controlling fan speed based on percentages, which are really measuring fan speed as the duty cycle of the fan’s motor on a relative basis, AMD has switched to controlling fan speeds on an absolute basis, using the measured RPM of the fan as their metric of absolute fan speed. This goes back to AMD’s concern over variance, as there is going to be some variance – and apparently too much variance – from fan motor to fan motor in how fast it can go, and consequently just what a specific duty cycle represents on a relative basis. Consequently by switching to measuring fan speed on an absolute basis there will definitely be less variation. as AMD is now controlling fan speeds by the very same metric they use to define that variation (RPM).

http://www.anandtech.com/show/7501/a...fan-algorithms