CPU temps keep rising and falling...

[Philippine Mango]

I'm running folding@home on my P4 w/HT on both "processors" so I have 100% cpu utilization. Problem is, while my case temps have been relatively stagnant with no change in airflow, the temps keep moving from 59*C to 61*C and back and forth... I have an IC7-G so the temp readings are a bit high but consistant.. I don't understand exactly how a CPU temp can increase from 59*C to 61*C and then drop back down if it's at 100% utilization and there aren't any noticeable programs taking up that usage.

The temps should be at their highest when they're at 59* since I'm running a gromacs core which uses SSE and a tinker on the "other processor" but magically the temps rise for a while then drop and I'm not quite sure why. It's getting really annoying because at 61*C the machine is considerably louder than at 59*C and I want to figure out why it's doing this, I even closed my antivirus but it did nothing..

 

[stevty2889]

Thats very normal. No temps sensor is perfect, it's going to fluctuate a bit. Voltages also fluctuate a bit, they don't remain 100% constant, and if the voltage is fluctating a bit, that can cause the CPU temps to fluctuate as well. Load temps aren't going to stay constant, Those are also pretty normal temps for a Prescott core. If it's a northwood it's a bit high. I mean if it was jumping from like 45c to 65c all while at 100% load, then I would be worried, but a 2c fluctuation is normal.

Exactly which CPU do you have, what heatsink are you using, what are your case temps, what other fans do you have in the case(intake and exhaust, PSU ect..). When is the last time you cleaned out the dust?

 

[Philippine Mango]

Northwood 2.8c that's overclocked, already mentioned that I have an IC7-G board, nortorious for high temp readings. I believe the sensors are consistant and don't normally fluctuate much because my fans are thermally controlled (separate from the system) and when the temps go from 59*C to 61*C then the CPU fan begins to spin faster. I have a thermaltake Volcano 12, Fan RPM goes from 4K to like 4.3K and that is a pretty big noise difference.

 

[Geomagick]

I think you've hit the nail on the head there. As CPU temp increases fan speed increases causing CPU temp to decrease, fan slows down cycle repeats.

I have found that thermally controlled fans to be more of an annoyance than a useful addition to a system in the past. I run all my fans at fixed voltages and this works pretty nicely.