Motherboard temp falls when CPU temp increase

[trinityworstation]

Hi,

I have a strange issue since I got my new system assembled last year.

The system:
Intel i5-2400 3.10Ghz
Crosair value-memory DDR3 4+4GB 1333Mhz
ASUS P8H61-M LX (Rev. B3)
XFX ATI Radeon HD4650 1GB
Seagate SATA 360GB
DVD RW + Portable Seagate 500 GB USB 2.0
Cooler Master PSU(SMPS) Extreme Power Series 500
Windows 7 Ultimate x64 SP1

The issue:
At idle state the CPU temp is b/w 40-46 degrees C, but the mobo temp is b/w 85-89 degrees C.
At working state when the CPU temp increases according to the workload, the mobo temp decreases proportionately. Strange, huh?
For ex: At 90-100% variable CPU usage the CPU temp will be around 70-75 degrees C and the motherboard temp falls down to 40-45 degrees C.

I have used Piriform Speccy and various other software to verify this, yet the temperature readings are the same.

What can cause such an issue?

Thanks in advance.

[ApPy10]

First of all can you try going into Bios and checking the hardware monitor which tells you what is the proper temp readings of the hardware peripherals installed. After that if it is still showing high temps, then I would recommend you to open up the cabinet and clear all dust particles from their and also check if some peripherals is not getting overheated as well.

[trinityworstation]

Thanks for the reply.

I have done the steps that you told me to no avail. How was it supposed to help? I did not have a CPU or Motherboard overheating issue. Please read my last post.

Research online has led me to understand that there is no temp sensor on my Mobo and hence the temp monitoring software are giving an erronous report. Reporting the CPUTIN temp instead. But it still doesn't explain the drop in the reported temp when CPU(core package) temp increases due various workloads (no overheating).

[T.J.]

That could be a combination of several factors. Not all motherboard sensors are created equal. Voltage and frequency crystals could be running slightly higher on any board. Same deal as the sensors. I've read somewhere that you really need to thoroughly clean off old thermal paste before applying a new layer. I have no idea if you have done that or not, and I usually don't clean the surfaces beyond what rubbing alcohol can do.

[trinityworstation]

That makes a little sense.

Now, I have a new issue after dusting the cabinet and cleaning the heatsink. When my CPU runs at 90-100% worload, temp rises to 85-87 degrees C. Previously, while running the same tasks caused temp rise to 70-72 degress C.

I tried refitting the heatsink several times, changing the thermal paste and even adding an extra intake fan right next to the CPU heatsink. Didnt work.

Either Im really screwed or it's just the sensors.

Any ideas?

[T.J.]

It could be a short of a faulty thermal sensor on the CPU, if the CPU is at 180F in the BIOS, which is possible since these CPUs can heat up very quickly, then it's possible the CPU cooler mounting is bad, even if it is solid. That symptom is common with a bad mounting of the CPU cooler. I would remount it, removing all the old thermal compound and use a small amount of fresh compound.