Re: What is likely cause of overheating CPU
- From: Paul <nospam@xxxxxxxxxx>
- Date: Mon, 15 Oct 2007 01:56:21 -0400
Graham wrote:
This is a continuation of the thread "Freeze-ups. Is power supply the
only remaining possibility?"
At this point I'm seriously considering replacing either the
motherboard or the CPU or both.
To summarize:
I acqired this computer with an unknown problem. The symptoms began
with persistent and almost immediate system freezes. This would happen
with any sort of high level activity, for example installing Windows
or runnning Windows. The motherboard had 2 visibly damaged capacitors
which I replaced. This made a major improvement, to the extent that I
thought it was "fixed". I later replaced the third cap in that
cluster.
The freezes returned but now usually take several hours to occur. I
didn't start monitoring the CPU temperature until after these freezes.
The reported CPU temp is consistently 30-40C in BIOS setup and 69-72C
in Windows. I was skeptical of these numbers but I think they may be
accurate. I ran for several minutes with the CPU fan unplugged and the
temp slowly rose from 70 to 92C. During that time the CPU was seen to
throttle back to about 56%. I also (with the fan running) aimed a hair
dryer at the heatsink and saw the temp rise from 70-74C with the fan
increasing rpm from the usual 3000 to 4500. I stopped the hair dryer
and the temp dropped to 70 with the fan coming back to 3000 rpm.
I have also replaced the heatsink/fan.
So, if something is causing the freezes and perhaps as a side effect
is also causing the overheating, would that fault likely lie with the
CPU or on some component of the motherboard?
I have tested the power supply with a multimeter while the computer is
under heavy load and the voltages are well within tolerance. I have
swapped out the RAM and hard drives.
No hardware conflicts reported in Device Manager, nothing obvious in
Event Logs, although I'm honestly not sure what to look for.
System:
Asrock M266A motherboard
Celeron 2.4
512 MB DDR
Thanks, Graham
Flip to page 24 of this document. See Figure 4.
http://download.intel.com/support/processors/celeron/sb/25174807.pdf
Your processor has a nominal Vcore of around 1.5V. It could be 1.475, 1.5,
or 1.525V. This was typical for the 0.13 micron processors (like my Tualatin
S370).
Figure 4 is a "load line". When the processor is not busy, it doesn't draw much
current. The operating point would be on the left hand side of the plot, on
one of those lines. When the processor is running Orthos or CPUBurn, it is
somewhere closer to the right hand side. As the current drawn goes up, the
Vcore becomes reduced in value, or "droops".
According the the lines, when the current drawn is zero, the processor is not
supposed to be operating at the specified VID of 1.5V. The processor is supposed
to be run at a little less voltage. And, in fact, since the current does not
drop to zero, you are actually a small distance from the left of the graph, so
the idle Vcore should be less than 1.5V.
You mentioned 1.6V, and if that was measured at idle, that is too high to fit
within the bounds of the upper and lower lines.
Your processor might draw 50 amps under load, in which case the Vcore value
drops by 0.135V below nominal. So, instead of seeing 1.5V, you'd see 1.365V
or so.
So it is important to note the conditions, during which the Vcore was measured.
It is either close to normal (if measured at idle), or grossly off, if it was
measured under load.
I agree, that either your processor or your motherboard is at fault. But the
processor managed to pass several hours of Orthos, which means it is not such
a bad character after all. I'd check out what is going on with the Vcore
voltage, as you vary the load conditions, and see if the voltage is
grossly out of whack. In which case, you might want to replace the motherboard.
If I didn't know which was busted, I'd have to start with the motherboard,
due to the excellent record I've personally witnessed over the years,
regarding defective processors. So if the Vcore remains too high, and there
is no BIOS adjustment to try dropping it, then changing the motherboard
is what I'd do next.
Paul
.
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