Possible causes of a CPU overheating?

November 15, 2010 at 09:23:15
Specs: Windows 7, AMD

A little while back my computer starting spontaneously shutting down. After a while I noticed it seemed to be related to heavy load which led me to suspect heat. I couldn't seem to get any readings within Windows but eventually I got around to checking in the BIOS and saw it was pretty close to 70C, the shutdown point and about the limit of the CPU when I looked it up. Eventually things got worse and I basically can't use the computer now.

It's an AMD system, not sure of the exact CPU (bit hard to get when the box doesn't stay up long) but the motherboard is MSI Socket AM2 N1996. The cooler is a SilentFlux Media.

To me the heatsink didn't seem too hot which led me to think of the sink, paste or connection not conducting properly, so I set about removing the sink. Unfortunately the CPU came out with it with a few bent pins but after some finicky straightening work I think it's in order again.

Anyway I cleaned with CPU and sink with Isopropyl, figured out this ridiculous contraption of a cooler and reapplied new thermal paste. However the problem persists.

All fans in the system seem to be operational, including case fan, PSU fan and the CPU fan inside the cooler unit.

While the sink was off (and the CPU being blown with a big external fan) I put my finger on the CPU and verified it was indeed really hot when the BIOS said it was, so I don't think it's a dodgy thermometer.

So that leaves me with a hot CPU and a not-particularly-hot heatsink. Which leads me to think either (a) something's dodgy with the heatsink or (b) my expectation of sink temperature isn't quite right given it's not solid.

I have read about these heatsinks not being simple lumps of metal but actually having liquid inside so I wonder about the possibility of leaking ... this system is a few years old I think (I bought it off a friend). Do these things need replacing?

Voltages seemed okay in the BIOS though I'm not knowledgeable enough to be sure.

Other than that I'm running out of options, not sure what to Google even. Thoughts?


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#1
November 15, 2010 at 10:10:32

Check in the BIOS again if you can and make note of the speed of the fan for the processor.You said the fan was spinning but It could be that the fan is not revving up high enough to cool the processor. It should be around 4200rpm if the processor is that hot, to try to cool it. If it isn't then I would say you need a new fan or fan/heatsink combo. Just my opinion. I had a similar problem and discovered that the fan on the heatsink was not spinning fast enough so I replaced the fan and all is well now.

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#2
November 15, 2010 at 10:47:14

It got to 1900 RPM off memory, however bear in mind this cooler, the SilentFlux Media, as its name suggests, is designed to be quite quiet (the comp was originally a media centre) and has a slower fan.

Were you using this specific cooler, or was the speed you suggest for a general-purpose cooler? Because it did definitely speed up, and I'm not sure what the max speed for this cooler should be.


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#3
November 15, 2010 at 12:46:14

So, you ran the computer while the heat sink was removed? Does the computer run at all now?

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#4
November 15, 2010 at 13:08:28

There was no problem. There was a very strong fan blowing on it (a house pedestal fan, much stronger than a CPU fan) and also the computer shuts down immediately when the temp gets too high. It took about 90 seconds to get to 60C without the heatsink.

It's a dual-core CPU, not one that dims your neighbour's lights and can replace your central heating system, and it's not a hardcore cooling system. The problem seems to be that it slowly generates heat, and it keeps building up.

It takes about 5 mins with the heatsink and CPU fan going, sitting in the BIOS (which I understand is 100% CPU), to start getting into dangerous territory.


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#5
November 15, 2010 at 13:19:45

Look at the link below to learn the proper way to apply thermal paste.

http://www.arcticsilver.com/instruc...


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#6
November 15, 2010 at 13:57:44

Actually I found a page that suggests 2100RPM is the normal speed for this fan, so yes, that may well be the problem. I'll have to look into it some more.

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#7
November 15, 2010 at 14:04:18

When using after market coolers you need to verify they are suitable for the processor they are being used on. AMD currently ship their retail processors with more than adequate heatsink/fans.

You should also verify the CPU settings for multiplier and voltage are correct. That can cause overheating.

Download SIW and use it to determine what processor you actually have.


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#8
November 15, 2010 at 14:18:27

Hi, thanks, the system has been running for years with these specs without issue. Mind you, it may have been running quite hot without issue and just started tipping over.

Now I know sitting in the BIOS is a high-load situation I'm a bit more comfortable running the PC as-is, I'll get the CPU information.

This page seems to be the fan for the unit, it says 2200RPM, but I'm not sure if that's max or normal speed.

http://www.directron.com/xsff9251.html


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#9
November 15, 2010 at 14:45:23

SIW indicated my CPU is an Athlon 64 X2 Dual Core 4000+ 2.1GHz, Brisbane core.

I tried to get a full dump but it took too long and the computer shut down.

It did say something about Original Clock 2100 Actual clock 2150 Original Multiplier 10.5 or something like that but I was limited in how much I could process in the limited time.


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#10
November 15, 2010 at 15:19:02

I got this out of CPU-Z:

http://ScrnSht.com/huxsvh

Settings seem to be normal.


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#11
November 15, 2010 at 15:30:36

Air cooled computers are the worlds best vacume cleaners. They suck in everything in the air and nothing gets out. When was the last time your system was cleaned? Dust breads heat.It's a vicious circle. You get a little dust. The airflow is cut down by a minute bit and heat starts to rise. The fans have to work harder there by pulling in more air and dust and the process starts over.

Make sure tou use the right amount of paste. Clean your entire system out. Put it all back together and run as normal. If the problem persist then start looking at replacing fans and what not. Having ran the system without the heatsink and fan was not a good idea. House fan or not. Air blowing on the processor does not transfer heat like a metal plate against it does. That fan blowing on it can affect the sensor faster than it does the actual temp. there by making the bios think the temp. is lower than it is. It can take less that a minute to fry a cpu in this way. Good luck.

Likely


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#12
November 15, 2010 at 15:44:27

It's pretty clean dust wise, I'm pretty thorough about keeping stuff clean, and I cleaned the CPU fan and so on when I replaced the heatsink.

What I really need to know at this point is whether the specification RPM of these fans (2200) is max or normal. Now I'm thinking max, which suggests that 1900 isn't too bad.

I'm not really sure about the right amount of paste, I'm not an expert in the area. I purchased a bunch of syringes of what I assume are single-uses so I'm guessing it's okay, but it took me quite a while to figure out how to reattach the heatsink so it's possible it got thinner but as far as I understand thin is desirable. I'll definitely do some more reading in the area.


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#13
November 15, 2010 at 21:42:31

You need no more than a spot the size of a grain of rice or two. As for fan speed there is no set speed that all fans should run at it depends on the fans. I have an older model aftermarket fan that spins at over 6,000 rpm sounds like a jet engine most of the time and the one I am using now runs around 2,500 rpm under normal load but kicks up to about 3,800 rpm under heavy load. Some fans are built more on the side of silence they spin less but have larger blades so they move almost if not the same amount of air.

Too much thermal paste is a bad thing. It can actually be detrimental to heat transfer not to mention it can squeeze out from between the heatsink and cpu and make its' way into the contacts under the cpu. This is not a more is better thing at all.

Likely


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#14
November 15, 2010 at 21:47:13

I purchased 5 of those little syringes of Arctic Silver 5 about 3 years ago. The idea was that for Christmas I was going to be building several computers, more than 15, and figured I would use it up pretty fast. I have since built over 50 machines and replaced a number of cpus' and still have over 2 full syringes.

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