How hot is too hot?
February 10, 2010 11:41 PM   Subscribe

Is it possible for my CPU to have been running over 100c without any warnings at all?

Building my first computer ever, and it seemed like everything was working fine? It's been running for a few hours.

Just out of curiosity I downloaded realtemp to look at the CPU temp. It was idling around 55c with no games or anything running at all. I booted up Team fortress 2 and it quickly jumped to over 100c! I didn't even know it could go that high? Can it go that high? I didn't hear any of the fans picking up. Everything from my end seemed like it was working perfectly. I got a bit jump and turned it off because obviously that's not normal.

Foxconn ELA LGA 775 Intel P45 ATX Intel Motherboard - Retail
Intel Pentium E6300 Wolfdale 2.8GHz LGA 775 65W Dual-Core Processor Model BX80571E6300 - Retail

I checked in the BIOS and it was reporting 95c

I've been reading a lot about thermal paste? I was told that the intel chips already have thermal paste on them? I didn't feel anything that felt like paste? Did I just fail at that?

Also, the stock intel fan/heatsink has a pretty crappy clamp system. I was only able to get three of the four firmly locked in place. Was that a problem?

I'm sure this sounds pretty lame to the tech elite. But I would appreciate any advice. I don't want to ruin this thing.
posted by lakerk to Technology (15 answers total)
Best answer: Ehh... 3/4 clamps means that the heatsink is not seated properly on your cpu. You should not be running it until you fix that problem. Seriously. I've not put in a cpu for a while, I'm not sure exactly what your clamp looks like, hopefully somebody below will. If you don't have an answer here, go to the forums there are good.
posted by defcom1 at 11:59 PM on February 10, 2010 [1 favorite]

Also, cpu coolers used to have a bit of thermal tape type material on the bottom of them (the side that touches the cpu) if that's just clean metal, and the top of your cpu is bare metal (I would expect the CPU to be) then you need to get yourself some thermal goo pronto. You MUST have something between the heatsink and the CPU to conduct heat away properly. A very thin layer. Google on how to apply the stuff. (Ehh. arcticsilver used to be the bee's knees. Haven't bought the stuff in years, probably something better now).
posted by defcom1 at 12:02 AM on February 11, 2010

The tabs on the clamp you can't insert are probably splayed wide apart, with one stuck on the top side of the board. You have to push them back together, possibly pushing them way over the other direction to try and bend it back to straight as best you can. Once you get both tabs through the board, getting it to lock will be easy enough.

Ya, the system sucks. Also yes, you could have been hitting 100C. Don't leave it that way, but don't worry too much, it probably hasn't been damaged yet.

The pre installed paste is probably on the heatsink side, not the CPU side, and that might be why you didn't notice any. If you are mounting bare heatsink metal against bare CPU metal, you need paste.
posted by Chuckles at 12:52 AM on February 11, 2010 [1 favorite]

The choice of thermal paste is really a very minor factor. Only worth a degree or two..
posted by Chuckles at 12:54 AM on February 11, 2010

That is, the differences between pastes are small, but the need for some kind of paste is great.
posted by Chuckles at 12:54 AM on February 11, 2010

100C is a perfectly believable number. Lots of semiconductors operate fine up to 100 or 150C. CPUs are generally not fine at that temperature, though; yours specifies a maximum back-of-the-die temperature of 74 C (which probably corresponds to a junction temperature of around 90C, from what I've read).

FWIW, the goal with thermal paste is to use as little as possible. Thermal paste is not as good a heat conductor as the solid aluminum heat sink. However, you really really want to avoid the microscopic air voids between the die and the heat sink that you'd have if you didn't use thermal paste at all, because air is a pretty bad conductor of heat.

There are things that people use instead of thermal paste— thermally-conductive squidgy silicone pads, etc. So it's possible that your heatsink came with something like that, but thermal paste is more typical.

Also, seconding Chuckles' point that having the heat sink clamps done right is important.
posted by hattifattener at 1:26 AM on February 11, 2010

CPU heatsink clamps are quite dodgy enough at the best of times; mis-fitted, they're much much worse. If you can't work out why yours doesn't fit, post lots of closeup pictures and somebody here will tell you which part is backwards or bent or in the wrong place.

Here's something I wrote recently about heatsink goop.

Just leaving out the goop can easily cause a CPU to run at 80°C when it should be 50, and I'm entirely unsurprised to find that a misapplied clamp could cost another 20 degrees.
posted by flabdablet at 3:25 AM on February 11, 2010

I see this at work all the time. The CPU produces heat, and the differential between that temperature and ambient temperature is what causes heat to flow away. A perfect heatsink would maintain the temperature at ambient, in effect, absorbing every "piece" of heat as it is generated. No heatsink would mean that the sirface of the processor would have to get REALLY hot (think 60W lightbulb) before the temperature differential was large enough to let the heat flow away. This is not a good solution, because the processor can't function at that temperature.

Alright, so your job in installing a heatsink is to remove as many barriers to that heat flow as possible. The first thing is that the heatsink has to contact the processor with as much area as you can muster. Your 3/4 solution is probably letting the heatsink sit crooked and only contacting (with any effectiveness) one corner of the processor.

Step two of that is that the heatsink has to be large enough and made of a material that conducts heat "fast" enough. Since it is the Intel-provided part, we can mostly assume that is right.

Third is the contact patch on the micro level. In a perfect world, you would machine the two metal surfaces so that they are identical, and that heat flow from one side of the junction to the other is functionally identical to heat flowing through a solid piece of metal. We can't do that (cheaply), so we try our best, and help the process by installing thermal compound. It is used to bridge the microscopic gaps in the metal, because it is a better heat conductor than air. But what you want to do is use the least amount necessary.

Because (back to my story), many of the compounds are very thick pastes. I see issues all the time where a heatsink was installed by the factory (or a dull technician) with a giant glob of the stuff. And the stuff is so thick that the heatsink never managed to press down on the CPU, and there was what amounts to a .5 to 1 mm layer of goop between the heatsink and cpu, obstructing heat flow.

What I like to do is put down a small glob of the stuff, install the heatsink, run the machine for a few minutes, and then shut it down and take the heatsink off. I check to see if the goop squeezed down properly and that there was the thinnest possible layer of the stuff on the mating surfaces, without any air gaps or obvious flaws. If all looks good, I clean it and reinstall with the same amount. If not, I modify the amount or the pattern until I get something that works.

But yeah, gotta fix that 3/4 thing first off.
posted by gjc at 7:20 AM on February 11, 2010 [1 favorite]

Assuming this is a stock CPU and heatsink, it came wit thermal paste already applied. It is in a very specific location and a very thin layer. It would only not be there if you got a defective item or you are using an aftermarket heatsink. But yes, it does need to be fully clamped down. You need to get that sorted before you start worrying about thermal paste, really.
posted by asciident at 7:23 AM on February 11, 2010

Response by poster: I fixed it this morning guys. The fan did have thermal paste already on it. CPU is now hovering around 30c and when I load games it goes up into the 50 c's . Thanks everyone for the help!
posted by lakerk at 7:41 AM on February 11, 2010

It's been a while since I've built my own PC, but isn't it possible the thermal paste on the heatsink came from the factory with a plastic cover on it? If it has, then you're not getting proper thermal goop contact. Need to remove that cover. As I recall, it's a thin film of plastic.
posted by bDiddy at 7:44 AM on February 11, 2010

oops! nevermind!
posted by bDiddy at 7:45 AM on February 11, 2010

It's good that you found the problem. As far as damage goes, Intel processors have on-die thermal sensors that will reduce the voltage and lower the clock frequency progressively if the temperature gets too high and can do a complete shutdown if necessary. This may cause glitches in performance but shouldn't do permanent damage.
posted by JackFlash at 10:38 AM on February 11, 2010

Glad to hear it. Enjoy your new computer!
posted by defcom1 at 2:22 PM on February 11, 2010

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