Reply #33: Just a few thoughts about any computer with these symptoms [View All]

[HamstersFromHell]

I've seen similar behavior in a few machines in my years in the business.

If it's an "out of the box" machine (i.e., brand name), you have to remember that they compete with each other on one common ground - price.

Therefore in order to still make a profit and be price competitive they cut corners *everywhere*. Nothing usually sub-standard, but often marginal if you add more things to your box that draws additional power or creates more heat.

I can remember Packard-Bell 386SX computers that came with such a marginal power supply (36w!!) rating adding 8 Megs. of RAM or a second hard drive would cause it to fail to boot entirely.

Intel factory heatsinks are notorious for being a bit on the marginal side, especially the Celerons. I've had client computers that would BSOD or shutdown for no apparent reason and opening the case would revel "normal" levels of dust, but removing the CPU fan from the heatsink would show the very small fins underneath completely clogged with dust. Canned air cleaned em up fine and resulted in a 30 degree or more reduction in CPU heat.

Another thing to look at is if the BIOS/chipset contains code for overheating shutdown. Some are set to merely throttle back at a certain temp., while others only offer a point at which to shut down entirely. Poking around in the CMOS might reveal that the shut down point is set much lower than what the CPU can actually stand. Intel usually says their CPUs will operate fine up to around 170 degrees F., while a lot of "heat monitors" in system BIOS' will default to shutdown at around 150 degrees...and it takes just a little heatsink dust to reduce efficiency to the point it'll trigger.

One last thing is if the CPU fan has 3 leads...the third is for an RPM monitor for the fan in the chipset, and is usually set to immediately shut down if it's not receiving the pulses telling it the fan's running. I've only seen it once, but a faulty fan intermittently not sending pulses can cause random shutdowns at any time. (Usually there is a setting in the CMOS to ignore fan rpm....you can set this to off temporarily to check if it's the culprit, but I don't recommend running the computer this way...it's there to prevent you cooking your CPU in the event of fan failure.)

Don't go replacing things until you've throughly cleaned the CPU heatsink...most of the dust will be hidden under the fan in the fins and not obviously visible without removing the fan from the heatsink.