I had to clean everything inside my PC today due to heavy dust accumulation and in the process remove the processor fan to clean it and the heatsink below it. However, while I usually mark the "right side up" for the fan, I'd forgotten to do so this time. While it made sense to keep the AMD logo on top, I was still not confident to start the PC without being completely sure. Google spouted advice hither and thither, but the general consensus appeared to be as follows:
- CPU fans should blow air into the heatsink.
- Case fans should bring cool air into the cabinet.
- Ideally case fans should either blow onto the CPU fans or blow across the heatsink vanes.
Hope this helps :)