Sudden CPU Heat

[feelingtheheat]

Hi all. I have an 18-month old Gateway DX4640 (product specifications), to which I have added an XFX GeForce 9800 GT card and a 550W power supply. 2 weeks ago, I experienced a motherboard failure. I ordered a new motherboard (from Skyline Engineering, a Gateway-recommended retailer), and received a model slightly different from the one original to my computer. I was able to successfully install it, but within about ten seconds of turning on the computer, my CPU, which had always run relatively cool, was running at 86C. Thinking that something had gone wrong with the thermal paste in the process of transferring the CPU, I tried reapplying my own thermal paste (Arctic Silver 5). Despite trying numerous reapplications of various thicknesses, cleaning both the CPU and the heatsink with isopropyl alcohol after each reapplication, the lowest I have been able to get the heat is 65C. So my question to you all is: what could be causing this sort of sudden CPU heat, and how can I fix it? Is it the fact that the motherboard I ordered is slightly different from the existing one? Is the CPU getting too much power? Thanks in advance for any replies.

 

[Onus]

Did you reset the BIOS to defaults? What CPU do you have? Is the HSF actually mounting flush on the CPU, or is any other component in the way, preventing it from seating properly?

 

[feelingtheheat]

Thanks for the reply jtt283. I have indeed made sure that the HSF is flush with the processor, and I have reset the BIOS to its "Optimized Default" values. The processor in question is an Intel Core 2 Duo E4700.

EDIT: I just had a thought. The air coming off of the processor seems pretty cool. Is it possible that the problem lies not with the CPU, but with the heat sensor? This would explain the fact that the reading is always exactly the same (85C), regardless of ambient room temperature. Is there some specific thing that has to be down when installing a CPU to ensure that the sensor does not go haywire?

EDIT 2: A BIOS update did not resolve this problem - my CPU temp is still a steady 85C.


EDIT 3: Well, it turns out that the motherboard that was provided to me by the Gateway-certified manufacturer did not have the right heatsink mounting bracket - my heatsink was not able to mount properly and so was not even contacting the CPU - after switching out the mounting bracket for the one on my old motherboard, I am now getting steady temps in the 20s. Thanks for the help.