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Processor Overheating Alarm
Last updated: 12/8/2001

Q. Recently an ambulance sounding alarm has started coming from my computer.  It only comes occasionally and lasts about 20 to 30 seconds. Should I have something checked?  I have an AMD K6 400 processor and the EP-58MVP3C-M motherboard...  What temperature should the CMOS alarm be set for an AMD K6 processor?

A. Your CPU is probably overheating!  If you get that alarm, immediately save your work, shut-down Windows, turn off the computer until the problem is fixed. You can burn-up the CPU, damage the motherboard, and even melt the thermo-conductive layer on the bottom of heat sink.  This problem is almost always caused by a heat sink-CPU fan which is defective, missing, not properly secured to the socket, or not rated/sufficient for the CPU.  The motherboard has two heat sensors (thermisters), one for the system and one in the middle of the CPU socket. You can see the temperatures and alarm threshold settings in the CMOS Setup (also, see Digest articles on  Motherboard Monitor Lite and EpoX's Unified System Diagnostic Manager (USDM)  for more details and motherboard monitoring software). If the alarm is going away (intermittent), I would guess the CPU fan has a bad bearing, which you should be able to hear, and is eventually coming up to sufficient speed to cool the CPU down below the threshold or the fan is running slow and the temperature is oscillating above and below the threshold (a condition which will eventually ruin the CPU, etc.).  A cable may have fallen into the fan and is popping out--not likely. The heat sink could have popped loose from its mooring on the CPU socket.  The fan in your power supply may be bad. You may have the alarm threshold set too low. Reload your CMOS defaults in the CMOS Setup. Check AMD's site for thermo guidelines for the CPU.  Don't use CPU fans with a sleeve bearing. Buy a quality fan with a ball bearing and a three-pin connector so it can be plugged into the motherboard and monitored.  Applying thermo grease under the heat sink would help, but I don't use it for socket 7 CPU's. I use heat sinks with a thermo-conductive plastic on the bottom of the heat sink.  Be sure to clean-up any bearing residue (black, powder-like substance); it can short-out the motherboard.  Do not clean a CPU fan with canned, compressed air while the fan is running.  The air from one of these cans is extremely cold and can cause the bearing to seize.  You may need an additional chassis fan (or a better case) if the computer is really loaded.  The motherboard may be defective.

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