I'm using an MSI B450M PRO-VDH PLUS with a Ryzen 5 5500 and the stock AMD cooler. I also have three TR120 case fans connected to SYS_FAN2 and an ADDA 92 mm exhaust fan on SYS_FAN1.
After changing the CPU_FAN1 temperature and speed points in the BIOS Hardware Monitor, the CPU fan began showing 0 RPM in the BIOS. The fan is visibly spinning, there is no CPU fan warning during startup, and restoring the original fan-curve values did not fix the reading.
In Windows, HWiNFO reports the CPU fan correctly at roughly 1,600 RPM while idle and above 2,500 RPM under load. CPU temperatures also look normal—around 45°C at idle and in the high 60s under stress. Both system fans report their speeds correctly in the BIOS and in HWiNFO.
Could this simply be a BIOS monitoring glitch, or is there another setting or hardware issue I should check?
1 Answer
Since the fan is spinning, the system is not reporting a startup CPU-fan error, HWiNFO sees a believable RPM, and temperatures are normal, the fan itself is probably fine. The BIOS tachometer reading may have become stuck or misconfigured after editing the fan curve. Try loading the BIOS’s optimized defaults first, then save and reboot. If the reading remains at zero, a CMOS reset is the next reasonable step; just record any custom settings first because it can reset boot order, memory profiles, and other BIOS options.
I restored the default fan-curve values already, but the BIOS still reports zero RPM. I haven’t cleared the CMOS before, so I’ll make a note of my BIOS settings before trying that.