Negative CPU temp reading failures (-84 °C) on B450 Tomahawk Max + Ryzen 3600 - Fan not spinning up


New Member
I detected a problem with a pretty new system based on a Ryzen 5 3600 and B450 Tomahawk Max. When gaming I logged sensor readings with HWinfo and while on game I saw that the CPU fan was not spinning up anymore. Instead it was around its lowest RPM of about 300 constantly. This absolutely didn't fit to the CPU temps at that time which were around 85 °C thanks to an aftermarket cooler (with the stock cooler they would have been even higher I suppose). I immediately stopped the game when I saw the temperature increase and unresponsive CPU fan to avoid CPU overheating.

What caught my eye next was CPU temperature reading in HWinfo from the motherboards sensor. Minimum value for this was -84.0 °C (???) and current reading didn't change from 0.0 °C anymore. I restarted HWinfo in hope this was only a problem with HWinfo but now the CPU temp reading was completely missing. The whole entry for the CPU temp sensor from the motherboard was gone. CPU fan was spinning only on its minimal setting.

Next I rebooted and finally CPU fan was spinning up again and also the temperature readings were back again. The next day I also noticed negative temperature reading directly from the CPU sensor (Tdie) (-11 °C). The only other benchmark software I had installed at that time were Ryzen Master and for a short time CPU-Z. But those weren't running at all when I logged readings with HWinfo.

Of course I am now afraid that maybe the motherboard is faulty and that this will happen again. I don't want to fry my CPU. Latest BIOS update is installed and everything is connected correctly. What should I do? Since doing the CMOS reset no more errors occured but I'm afraid that maybe the board could have a defect. Is it even possible that benchmark software causes too low CPU temperature readings from mainboard sensor which in effect leads to the fans spinning to slow?

So I guess it's very unlikely that benchmark software could have such an effect on temperature readings and fan speeds? Thats just what I was afraid of.
That's quite unlikely, but to be sure try only an MSI tool (CC or One) without any other monitoring tools to see if the problem will appear.
Thanks for the response. Just wanted to give a quick update. Since removing all unnecessary software like Ryzen Master and MSI Dragon Center and doing another BIOS update and CMOS reset I couldn't reproduce this strange temperature readings again. Even after hours of logging, temperatures seem to be normal. Guess that this was some kind of software quirk as a faulty sensor would likely have stopped working again. Nevertheless going to keep an eye on it.