Strange fluctuating fanspeed in HWMonitor

Liqourice

I have a small concern that I don't know what to make of.

When I have HWMonitor running I see that sometimes it reports the cpu fan as having 0 rpm's.



It shows this just breifly, for about half a second, then it goes back to about 2650. The intervals between this seems to be different as well. Sometimes it's just a few seconds, sometimes it's up to 15 seconds in between. CPU and core temps fluctuate one degree up and down as well but if this has anything to do with this I don't know, it might just be normal fluctuation.

I don't know what to make of it. Is it perhaps HWMonitor that's at fault? It doesn't happen at once after a reboot either, it takes a few minutes before it starts.

I've seen this since I removed the speed adjusting box that came with the fan (Zalman CNPS9500 AM2). Now it's connected directly to the cpu fan connector. I want it like this since the fan runs 200 rpm's faster than it does with the adjuster on, even if it's on max, and I hardly ever turned it down before anyway.

Tried with C'n'Q active and inactive but the same thing. Haven't disabled C'n'Q in bios though, gonna try that next time I reboot and see if that fixes the problem.

Will probably hook the adjuster on again to see if the problem goes away as well. If it goes away I really have no idea what to make of it...

Any ideas?

Oh, and I'm asking in here since I worry that it might be a hardware issue.

mkk

Compare with some other program like Speedfan or so, but I'd expect it to simply be some sensor glitch. If the fan really did spin down from 2600rpm I'm sure you would notice the variation in the noise level.

Liqourice

No other software indicates any change, more than a few rpms. Speedfan doesn't and I've left the hardware monitor in bios on for 10 minutes to see if it does it there but it didn't.

THe fan doesn't lose power since the light is on at all times. I can' hear a slight difference in tone but that might just be some acoustic variance from all 4 fans together so I'd have to disconnect all case fans to listen for that. I've got to get some kind of use for that perfect pitch sometime.

Hopefully it's just as you say a sensor glitch since speedfan doesn't seem to register it. Gonna check a few things though.

mkk

That sounds promising at least. I'd use that Zalman fanmate regulator by the way, but perhaps that CPU can use the cooling that the full fan speed gives it.

Liqourice

Yes, that's why I use it like this, I need the extra cooling I'm afraid.

Though. Disabled C'n'Q in bios and now the issue is gone. The fan also runs about 50 rpms less, strange.

mkk

Ah, I guess Cool'n-Quiet changed the behavior enough to confuse at least one monitoring program. Though unless overclocking I'd want to keep that feature on to save some watts I guess. Now that you mentioned it I recall reading about confused sensor readings from Cool'n-Quiet on some motherboards.

Slight variations of fan speed like 50rpm +/- and intermittent tonal signature shifts can occurr from the +12V line fluctuating slightly between load and idle power draws, with fans that spin as fast as that one. The same common voltage variational changes can also be noticed in a system that produces hearable coil whine from some component, modifying the amplitude as it occurrs.

Liqourice

Well, I just added another 140mm fan in the bottom of the case and this issue is back, as well as HWMonitor is reading the speed of that new fan as around 2900 when it's only rotating about 650 so I'm writing this off as a problem with HWMonitor.