I am hoping for some ideas here. I have a small form factor PC that uses the BLKDG45FC Intel motherboard. Consistently it has periods of several minutes where the CPU fan will throttle up to full speed, only for a few seconds, then throttle down to a near silent RPM. This goes on for perhaps 30 minutes, and sometimes is followed by a period of time, say 20 to 30 minutes, where the fan is near silent. There is no apparent pattern here. In a quiet room, the throttling is very annoying, and causes worry over impending failure of some sort. I have been trying to find the cause of this issue and fix it, but to no avail. I thought I would list all that I have done, in hopes of leaving only those ideas that I have not thought of to be pointed out to me.
First, CPU fan replaced. All heat sink fins cleaned very well. New thermal grease added between CPU fan and CPU. BIOS upgraded to latest version. Motherboard replaced. PC is running current anti-virus software and has also been scanned and found clean from malware. Task Manager monitored for activity during fan high RPM, but none found.
Any ideas would be appreciated. The PC is running Windows 7 Pro, 32 bit OS
I had been monitoring the task manager, but it shows everything in idle, even when throttling is occurring. I see the CPU at 97-98% for System Idle Process. Really, cannot find anything software that is causing this. I am growing suspicious of CPU. It is dual core. Is there any way to know if CPU temps are abnormally high?
It might just be the way the fan controller is designed, it goes very slow to be quiet, then at some point has to ramp to cool the CPU, then goes quiet, then ramps up again. You may have settings in the BIOS that can adjust this.