Feverish Processor

September 21, 2007 6:28 PM

I have a Pentium D 925 that's running from 56 at idle and spiking to 78^oC according to Everest and even hotter according to the BIOS. How bad is this?

No instability or other problems, but the fan is running through speeds like mad every time I try to do something interesting. The cooler is secure (I checked each leg and they're tight) and the paste applied sparingly. Will I hurt this by continuing to use it until I get another heatsink? What inexpensive heatsink will keep this cool?

posted by IronLizard to computers & internet (28 comments total)

That's within spec. Those Pentium Ds do run hot. If it really bugs you, the Core 2 Duos should be a drop-in replacement and fix most of your heat woes.
posted by marionnette en chaussette at 6:48 PM on September 21, 2007

Are you sure? I though it was max of 63.4?
posted by IronLizard at 7:05 PM on September 21, 2007

63.4 is the max temp of the air in the case near the CPU, not the max CPU temp.
posted by sanko at 7:14 PM on September 21, 2007

I think you're misunderstanding just which 'case' intel is refering to.
posted by IronLizard at 7:43 PM on September 21, 2007

That's hot. Try blowing off the heatsink/fan with compressed air. That can lower things by 10°C if the coolers are dirty.
posted by Nelson at 8:54 PM on September 21, 2007

Already done (mostly clean before I put it in, 115 psi through a small tube works wonders on dust and small children). I also added a fan to the front of the case, lowest temp is still 56. With light use right now it's hovering at 60.
posted by IronLizard at 9:04 PM on September 21, 2007

What is the room temp? What is the case temp? How is the airflow in the case? Is it a new install?
Is the cpu fan seated properly?
posted by jockc at 9:27 PM on September 21, 2007

Oh I see you checked the fan. Those 775 fan mounts are a pain. I switched to one with a back plate; I could never get it tight enough with the plastic pins.
posted by jockc at 9:32 PM on September 21, 2007

YAh, they suck. The room temperature, according to my totally inaccurate thermostat is 73F. Other PC readings as follows:
Motherboard: 44C
Unknown: 52C
Unknown: 39C
Proc fan: 1900rpm at 57C
Rear cooling fan: 1500rpm
posted by IronLizard at 10:02 PM on September 21, 2007

Also, I read somewhere that if the heatsink was too hot to touch for three seconds or more there was a problem. I quickly powered down and grabbed it. It's lukewarm. So either everything is lying to me (the bios used to report 55C for the 2.6 celery that used to be in here, it reports low 60's for this) or the heatsink's not sucking up enough heat. Or something.
posted by IronLizard at 10:07 PM on September 21, 2007

Thermal throttling or general instability should kick in before any damage occurs. 78c's very high, but that's probably from the thermal diode, which is going to read quite high anyway (because it's actually on the die, as opposed to a sensor under the socket), and may well be badly calibrated.

How sparing were you with the paste? If you were too sparing and the heatsink isn't applying enough pressure there might be an air gap insulating it from the heatsink.

My favourite heatsink atm is the Scythe Mine, but I'm all AMD so have no idea what the mounting's like on Intel sockets.
posted by Freaky at 10:26 PM on September 21, 2007

I used roughly a 3rd of an inch round squeeze right in the middle, following this image. No sign of instability yet, but I haven't really pushed it at all. Rather afraid to really, after seeing that AMD explode on video. I know, this one won't do that, but it's enough to make you pause.
posted by IronLizard at 10:35 PM on September 21, 2007

It sure sounds hot. My similar CPU never got that hot, but it did get to at least the high fifties. The intel stock heatsink sounds like a jet engine anyway, so I would get rid of it just for that reason (and I'm normally very cheap!).

Feel different parts of the heatsink. Depending on the fin design, I wouldn't be surprised if fin tips are pretty cool to the touch even when the CPU is 75C..

I would say you want an Arctic Freezer 7 Pro, but the price may have gone up a bit too much. I'm pretty sure I got mine for $23 (CAD, and at the time it made a difference), that wasn't even the cheapest price in the city, at the time. At ~$30, there might be a cheaper workable solution..
posted by Chuckles at 10:54 PM on September 21, 2007

I used roughly a 3rd of an inch round squeeze right in the middle,

Wow, that's about 20x too much. All that's needed is enough to make the thinnest of thin layers between die cap and heatsink, to fill and even out any irregularities. A little tiny dollop, not much bigger than a match head and smoothed down to an almost transparent layer, is all that's needed.

Still, your temps don't sound too high - I've got an Athlon XP 2400 that reports around the same temps during summer, and as someone said Pentium D's run hot. I've also learned to have only minimal faith in any of the system-reported temperatures; they're all pretty inaccurate
posted by Pinback at 11:21 PM on September 21, 2007

Chuckles: They're 19.99 at newegg now. I think I just found my new cooler, thanks. Not one local store I've checked has anything rated for more than the P4 that isn't some overpriced monstrosity.

Pinback: I believe it, but that athlon is rated at a much higher operating temp from AMD. (85C max). I'm getting rather comfortable with it because everything seems to be working great right now.
posted by IronLizard at 11:44 PM on September 21, 2007

im surprised at this 85C rating. all of the asics i've worked on have been taped out to meet timing at 125C (junction temperature) and slow silicon. i wonder if intel isnt sandbagging a little bit in their public documentation.

i know most xilinx parts are only rated for Tjmax=85C; maybe the same is true of CPUs. anyway how well do these pentium Ds overclock? that should give you some idea of the margin available.

anyway its true that the pentium D runs quite hot. its probably still worth the effort to redo the thermal grease and try a new heatsink/fan.
posted by joeblough at 12:09 AM on September 22, 2007

Ok, if it's running that hot but the cooler is lukewarm, you absolutely, for SURE, have a contact problem between the cooler and the chip. If you have any way to ratchet up the tension some, that would be good. Otherwise, you should consider buying an aftermarket cooler with a backplate.

Note that to install a backplate, you'll have to completely disasssemble the computer and pull out the motherboard. This will be a pain. But your computer will probably run faster, because you're probably being thermally throttled, which I think kicks in at 80C.

Remember: 78C is 173F, which is scorchingly hot. A likewarm cooler in that circumstance is not working. This is 100% certain.
posted by Malor at 12:28 AM on September 22, 2007

OK, so how do I make absolutely certain this cooler is on as tight as it will go? I'm ordering the Arctic 7, but I'd like to make this work until it gets here. Thanks everyone.
posted by IronLizard at 12:37 AM on September 22, 2007

I took the heatsink off quickly after shutting down and the processor wasn't much hotter to the touch than the cooling fins. After reapplying the thermal paste even thinner and spreading it out, it idles a degree lower (55) and seems to stop well short of the 78 it had reached before (68-72, didn't go over 70 while loading photoshop, inkscape and word all at once). Still too warm according to the specs, but it suppose it'll do for a few days. Though the touch test on the processor makes me lean strongly to a badly calibrated sensor, I'm getting another HS just to be safe. Thanks again for the help.
posted by IronLizard at 2:27 AM on September 22, 2007

Thermal paste is easy to get wrong. If your CPU temp is way higher than your heatsink temp, you probably have too much, too little, or air bubbles.

The way I put thermal paste on:

1. Put a match-head-sized blob right in the middle of the CPU. Do not spread it around with a tool, just leave it as a blob.

2. Push the heatsink onto the CPU, and smoosh it back and forth and sideways and round and round to the greatest extent allowed by all the plastic foolery that surrounds it. Keep the heatsink base flat on the CPU as you smoosh - don't let it rock. At some point you will feel the slipperiness give way to an almost suction feel. That's when you know you're nearly done.

3. Take it apart and look at it. You should see a very thin (to the point of being translucent) coating of paste all over the CPU surface, with just the barest scraping over the edges.

If that is indeed what you see, then clean it all off the CPU and the heatsink and do it again exactly as before, skipping step 3. If there's a heap over the edges and/or the coating is thick enough to be opaque, clean if off and do it over, including step 3, starting with a smaller blob of paste. If there's a round area of see-through paste that doesn't make it to the edges of the CPU, clean it off and do it over, including step 3, with a bigger initial blob. If there's a round area of opaque paste that doesn't make it to the edges of the CPU, clean it off and do it over, including step 3, with the same size initial blob but spending longer in step 2.

4. Apply clamps. If the heatsink rocks off the CPU as you apply the clamps, start over from step 1.

Do a few tens of these, and you won't need step 3.

The rationale: if you spread the paste with a tool before putting the heatsink on, or if the heatsink and CPU get separated after the paste is applied, it's very easy to end up with air bubbles trapped between CPU and heatsink; these create hotspots you definitely don't want, as well as lowering overall thermal conductivity.

As Malor said, if your CPU is hot and your heatsink is only lukewarm, the problem is a lack of thermal contact between CPU and heatsink.

You can get a rough idea of how well calibrated your temp sensors are by powering up without the cooler in place, using your finger as the heatsink, and checking the BIOS temperature report. If the BIOS says 60°C or above and you're not yelping in pain, the sensor is reading high. 50°C is about as hot as most fingers will tolerate for any length of time.
posted by flabdablet at 5:46 AM on September 22, 2007 [1 favorite]

It should go without saying that running with a finger for a heatsink should only be done for as long as you're not yelping in pain. Be prepared to turn it off pretty quickly.
posted by flabdablet at 5:50 AM on September 22, 2007

I start with a little blob of Arctic Silver 5 about the size of a grain of rice. I spread it super thin using a credit card. I am using the Zerotherm btf 90 cooler which is kind of expensive, but seems to work well keeping my (also high) temps done. Unfortunately due to location this room is the hottest in the house. Room temps in the summer can be up to 82-83F. When I attach the cooler I due one turn on each screw around and around until they are all tight.

I am running a Q6600 at 3.0 ghz and my loaded core (aka tjunction) temp is about 70.
posted by jockc at 8:33 AM on September 22, 2007

I took the heatsink off quickly after shutting down and the processor wasn't much hotter to the touch than the cooling fins. After reapplying the thermal paste even thinner and spreading it out, it idles a degree lower (55) and seems to stop well short of the 78 it had reached before (68-72

I knew I should have clicked through to see that thermal paste picture :P   Anyway, flabdablet has covered that.. Contact was an issue, and probably still is, but the sensor also seems wrong.

Under controlled conditions, if you make an improvement, the temperature reading change under load should be about 2.5x the reading change under no load (because the CPU power is roughly 2.5x higher under load).
However, if that 1C improvement at idle is really 1.4C, and the 72 isn't under as high a CPU loading as the 78 was measured at.. Well, then the sensor starts looking better.

Increasing pressure will help too. Unfortunately, when it comes to pressure, the cooler I pointed out is no better than the stock Intel heatsink (better in every other way though!). If you get the thermal paste right, I think the benefit of increasing pressure is fairly small. If you put too much paste, pressure will help a lot (because some of the excess paste is squeezed out).

powering up without the cooler in place, using your finger as the heatsink,

Don't do this on Socket A Athlons! Probably too old for anyone to care much about now, but they burn up very quickly.

You can accomplish a similar effect less radically by intentionally leaving the heatsink's fan unplugged and only holding it in place manually, for quick removal (still not for Socket A Athlons though, really!). Power the system up and wait for the heatsink to feel lukewarm (or the temperature reading to get to 75), note the temperature, then quickly shutdown and stick your finger in the middle of the heat spreader on the CPU (and the heatsink base too..). This should help you figure out if the sensor is wrong, or if the heatsink to CPU contact is poor, or whatever..
posted by Chuckles at 9:24 AM on September 22, 2007

Room temps in the summer can be up to 82-83F

Oh man, I'm screwed. It regularly gets to almost 90 in here mid-summer unless the a/c never shuts off. It was 80 in here yesterday before I cranked it up because of this little problem. As for the spike temp, I managed make it go up to about 75 today but it takes a lot of work. I'm going to do the paste once more.
posted by IronLizard at 12:23 PM on September 22, 2007

Oh, and What is I bend the sink's legs upward ever so slightly?
posted by IronLizard at 12:24 PM on September 22, 2007

Err, what if, I mean.
posted by IronLizard at 12:25 PM on September 22, 2007

It isn't a terrible idea, but be careful about the alignment. Well balanced pressure is a lot more important than overall pressure. Mounts for PIII's were self equalizing/leveling (they rocked on a bump that sat right over the die), but I don't think very many s775 mounts are.
posted by Chuckles at 1:10 PM on September 22, 2007

Just to close it out, I picked up an aftermarket coolermaster (not much else was available locally for less than 40 and I got in a rush) and it's staying in the fifties for the most part and the fan's nowhere near it's limits like before. I think it could be better if I hadn't left the cooling compound (or pad) that came with it but I'm going to leave well enough alone for now.
posted by IronLizard at 1:56 PM on September 23, 2007