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Computer instant shutdown Core i7 940, Asus Rampage II Extreme

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December 6, 2011 10:43:19 PM

I own a home built gaming PC with a Core i7 processor, the motherboard is an Asus Rampage II Extreme. I have had this machine running perfectly for around 1-2 years however I now have a problem where the PC instantly shuts down around half a second after I press the power button. I have tried using a different PSU and cross tested all other components apart from the CPU and motherboard. I have identified the problem to be one of these two components however I cannot cross test further since I do not own another system this powerful. If I run the PC with no processor attached it appears to run without shutting down, the same is true when I unplug the 8 pin auxiliary power cable for the processor. I am unsure what the next step should be since I cannot find which component is faulty and neither manufacturer will accept a warranty return as I cannot prove that either product is at fault. Today I re-seated the processor, and the PC worked, I was able to install Windows again and use the PC, I had no trouble restarting the PC either, however, when I unplugged the mains power cable from the PSU to install another HDD, the problem re-occurred. When I re-seated the processor, I replaced the thermal paste too since I thought an overheating problem may be causing the issue. I also had an existing issue with a temperature sensor on the motherboard, this was shutting down the PC while in use after a random amount of time due to the overheat protection. I am assuming the sensor was faulty since it was displaying the north bridge temperature as 90+ degrees celsius. Not sure if the aforementioned fault could be related to this issue but I did turn off the overheat protection for the north bridge to prevent the PC from the spontaneous shutdowns.

Does anyone have any suggestions on what the issue could be or how I should deal with this?
December 7, 2011 12:26:11 AM

sounds like a faulty Motherboard. incorrectly reporting temperatures.

CPU's are VERY REARLY ever faulty.
a b B Homebuilt system
December 7, 2011 12:41:51 AM

Have you tried breadboarding the system? If not, that should be your first step.
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December 7, 2011 5:37:07 AM

I have tried running the PC outside a case and this had no effect however I believe I may have identified at least half of the problem. Because the problem re-occurred after unplugging the mains cable, I decided to try replacing the BIOS battery, now I can boot as far as BIOS on most occasions but it is still suffering from the spontaneous shutdowns because of the north bridge overheat problem. All I can do is leave it a while and hope that when I next boot I have time to disable the overheat protection on the north bridge.
December 7, 2011 6:04:10 AM

Just a quick update... I have been able to turn off the overheat protection and I am now installing Windows. I have also tried removing the mains power cable then re-starting and the PC appears to work. Assuming the fault was a combo of faulty sensors causing shutdown and drained BIOS battery losing my BIOS config and allowing the shutdowns.
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