CPU usage 100% when hot

[Kleffman]

I have never seen anything like this before...

When my cpu gets "hot" around 39C (not very hot) the cpu usage under task manager is showing 100% and everything is brought to a crawl. music skips, etc. Then I put a floor fan next to my computer, open the case, and the cpu goes back to 0%, where it should be at idle. see the linked screenshot, when usage dips is where I turned the fan on and guess where I turned it off...

What could be the problem here. I have a pentium 4 630 which is a hot running processor but I just recently installed a Zalman cooler to try and cure this...didn't help! how does usage have anything to do with temp!? this is all at idle (except maybe playing music)

http://img157.imageshack.us/img157/3600/cpuusage1tx.jpg

Thanks for any suggestions!

 

[LawnBoy]

First, "idle" is a very relative term. You usually don't know when your virus or spyware scanner is going to kick in, or when windows is going to swap a bunch of stuff to disk, or update itself, or any of a thousand processes that don't require user action. It could be that the processor finishes it's job about the time you start cooling it.

If you are confident that tempurature and processor usage are related, you need to increase the airflow in your box. you may have the greatest heatsink in the world on that proc, but that sink just dumps the heat into the enclosure, it doesn't vent it to outside.

 

[Johnthephoneguy]

Water cooling is the way to go, it dropped my temps 11 degrees.

 

[Maugwa]

Was this problem happening prior to installing the Zalman? If not, then you may want to check to make sure that you have the Zalman fully seated and secured as well as use thermal paste.

 

[Maugwa]

BTW: 39 C is not really that hot for a P4 Cpu now days. If that is your max temp, then you don't have much to really worry about. Just need to find out what's causing your cpu to shoot to 100%. Are you running Folding@home or any other program that runs when your system is idle?

 

[franklin97355]

P4 CPUs will throttle back their cycles when they get hot to try to save the chip. It could be the chip thinks it is hotter than it really is or the temp reported isn't as high as the actual temperature. As Maugwa says check the heatsink and make sure you're not running processes in the background that are using extra cycles.

The answer is "42"

 

[Kleffman]

Thanks for the replies guys...I'll attempt to answer them all.

first, yes definitely heat and cpu usage are related, as much as it makes no sense to me. I've done it on multiple days many times. It starts acting up, I check task manager, cpu is 100%, I open the case and turn on a fan...cpu usage goes down and all is good. If I don't, it stays at 100% as long as it wants.

This was happening prior to the zalman, and the zalman did make it run cooler than it used to, but hasn't solved my problem.

Agreed, 40C is not very hot for a p4 630. So I guess the issue is why does my cpu go nuts when it's around that temp. where is the heat sensor located, on the chip or on the motherboard? There are no extra processes running in the background besides what windows loads at startup. And I keep those to a minimum. It just does it when it gets hot, and with the weather right now this is often.

Any suggestions? mobo bad? cpu bad? the zalman actually sends it's air right to the case exhaust fan and a lot of air is coming out, my temps aren't that high. AHH! what do I do?

Thanks so much for the suggestions.

 

[LawnBoy]

How hot is the inside of the case getting? It could be some other chip or a drive is getting hot.

 

[Kleffman]

that temp generally reads around 40 too. I'm using speedfan for this, is that program generally accurate? maybe if I quickly restart and check the temps in the bios it'll be more accurate. any other temp programs you recommend? my 6800GS graphics card reads a core temp of around 50C when it's hot. it's a lian li case that is pretty spacious I don't know what else could be getting hot.

 

[Kleffman]

I just had a new thought...anyone have an opinion on this?

It seems like it got worse after I installed a tv capture card, which is somewhat close to the video card. if the video card is getting hot does it offload processing to the main cpu to save itself? that could cause all this, and then the floor fan would help, and would also explain why my new heatsink didn't help. Do video cards do that to decrease their own heat? It's not like I'm playing video games, but just for standard video output maybe it's getting too hot?

Thanks guys,

Justin

 

[satrow]

It is not unkown for resource-hogging PCI cards (Soundblaster esp.) to create problems when installed immediately below the AGP slot; somehow these slots seem to share some resources (I'm not sure if this applies to PCIe gfx slots as well).

If this is the case, as Lawnboy suggested, it may be another chip that's getting too hot - the Northbridge? Does this have a heatsink? Can you add a fan to it?

Could you re-order the cards in the PCI slots or free up the one below the gfx slot for troubleshooting purposes?

 

[Kleffman]

Worth a try for sure, I'm not sure how it explains the whole heat = cpu usage issue though. My northbridge has a small heatsink which isn't anything too awesome. I suppose I could try to more adequately cool it...

 

[Kleffman]

I just felt the heatsink on the northbridge and it's practically hot enough to fry an egg...does anyone think that could cause the problems described? if the northbridge is overheating why would that cause the cpu usage to go up?

 

[tf1]

Reading this thread I can't help feeling that you are looking at this backwards and that removin ghte case and blowing with a desk fan is really a red herring. If the CPU is running at 100% (presumably reported by Task Manger), then the temperature of the CPU is fine and the Zalman cooler is doing an excellent job.

The real question is what is using up the CPU. Run Task Manager, select the Processes tab and see what is gobbling the CPU. That should give you the clue you need.



Regards: tf1

 

[Kleffman]

See that's the thing, I figured the same, and with speedfan I can see the cpu temp is around 35-40C. However a fan always solves the issue, ALWAYS. So something must be overheating. As for the CPU usage when I say 100% it's actually only 50%, because it's one side of the hyperthreading being used up in the display. But having that maxed out is enough to make music skip, folders drag badly, etc. Now, trying to find the process at fault was one of the first things I did, and the funny thing is it's always "system idle process" that's got 99% of the cpu, with the exception of maybe firefox or winamp at a few percent if I have a couple things open. I've ran virus scan, and haven't ran adaware in awhile. I can try that. But if a process were hogging all of the cpu it would most certainly show up in task manager I would think.

I really appreciate all the input guys, thanks. Any more ideas keep them coming.

Justin

 

[tf1]

Okey dokey. What happens if you leave the case open and run the PC doing your usual stuff (ie no desk fan blowing over the PC)?


Regards: tf1

 

[Kleffman]

Well, generally I have the case open with the fan blowing directly into it to solve the issue. If I turn the fan off and just leave the case open it really depends how hot the room is. Mid day when it's hot I still have the issue. When it's cool at night it's not such a problem BUT it can be if I start doing something that makes it work harder like watch movies. However with case open, floor fan pointed at it...the issue never crops up no matter what I'm doing.

I think what concerns me most is not only finding out what is overheating, but why it causes the cpu to take off. Unless I'm looking at it all wrong, like you said. But I'm pretty fixated on the fact that a fan "solves" the problem.

Thanks again!

 

[LawnBoy]

why it causes the cpu to take off

Let's say a chip is overheating to the point of becoming intermittent. The proc attempts to perform some function with that chip, it tells the chip "fetch data from address xxxx" and the chip responds with "request failed" or worse, a nonsensical response. The proc now has to read the BIOS to see what steps to take to recover from the error, and then try to fetch that address again. Over and over.

A chip can be electrically functional, and not cause a reset on the motherboard, but still fail a logical operation. It's not common, but it can happen.

 

[Kleffman]

That's a good explanation, thanks.

well I hate to keep adding fans inside the case. Maybe I can first try to reseat the northbridge heatsink and chipset heatsink with fresh arctic silver...both are cooled passively. The motherboard is an Asus P5ND2-SLI if anyone has experience with it. It has a lot of features but so far doesn't seem to operate that wonderfully. I suppose maybe the fans that came with my case aren't very good too, and could be replaced.