Where are temp sensors located on a motherboard?
 

Today I overclocked my A64 3000+ from 2.0GHz to 2.5GHz and I just ran Prime95 to test out the stability.

Within ten minutes one of my temperatures shot up from 40C to over 60C.

MBM tells me that it sees three temp sensors on my board, one for the CPU, one for the mobo, and a mysterious "auxiliary." The auxiliary is the one that shot up over 60C. I have both the mobo chip and the CPU watercooled, and by the looks of it, whatever is the aux is definitely not watercooled because it's been ten minutes since I stopped Prime95 and the aux temperature is still at 55C.

Any ideas what part of my mobo this aux sensor is measuring? I have a Shuttle AN51R, nForce3 250GB, and the sensor in question is IT8712F #3.

I think that auxiliary is power supply?

Well, my power supply is not a thermistor fan PSU; there's a dial to manually set the fan speed. I've had the PSU fan on high for the past few minutes and the temperature (55C) has not budged one bit.

mosfets? not sure at all

mosfets it seems to be. Someone from anandtech pointed me to a german page and I managed to find the location of three of the thermistors, which is weird, because they are for case temp, MOSFETs, and CPU... no mobo chip. Motherboard Monitor is only reading three temps too, MOSFET, CPU, and case.

In the following picture are the locations of where the thermistors should be. The case and MOSFET ones have been positively identified, but I can't see one for the CPU and neither my eyes nor my software can see one for my mobo. I'm new at this thermistor location stuff. Is it odd to not see a thermistor for the CPU and also for a mobo temp reading to be nonexistent?

http://img.photobucket.com/albums/v4...hermistors.jpg

The CPU has an onboard thermistor, if the case temp and the mosfets have been identified, then the last one is the southbridge.

But that's the thing. My temperature monitor displays three temperatures: The CPU, the MOSFETs, and the case temp. There is no temperature for the southbridge, which I find really odd. Is there supposed to be no thermistor and temperature reading for the southbridge?

I've never seen a SB thermistor. The 'Case' temp thermistor is usually randomly placed away from the really hot stuff....in your board top right where you circled. Your cpu thermistor is in the core, better than the old in socket ones.

My shuttle has a PWR thermistor surrounded my mosfets like yours. It also spikes under heavy load, like yours. I sat a downvolted 92mm fan upright on my vid card, facing them and my passive NB HS. It keeps it all a bit cooler w/o extra noise.
http://216.77.188.54/coDataImages/p/...ugust04014.jpg

Good to know that someone else has the same spikes :)

Haha, yeah, I did the same thing as you did, basically sitting a fan on my video card. Eventually I'll figure out a better method.

Should I worry about not knowing the temp of my southbridge? I'm definitely overclocking the "FSB" at 1GHz right now, but the southbridge is watercooled.

One thing that I'm concerned about is the CPU temp that Motherboard Monitor displays. In the BIOS, the CPU temp is around normal, about 40C. Right after booting into XP, however, MBM shows the CPU temp as 70C+! I've tried other temp monitors like speedfan and MBProbe, but all do the same thing, so I've been putting an artificial correction of about -31C to the 70C+ reading, making the final reading around 40C. I've got the latest BIOS, and this is the second AN51R board that I've gotten with the same problem. Should I be worried about this incorrect temp reading?