What's the cause of 20c cpu temp difference between idle and load?

I appreciate the advice given in another thread on this forum, and should be getting my Ceramique next week. My main question, so I don't waste money buying another heatsink and fan, is this: Is a 20c difference between idle and load a sign of poor thermal compound/improper hsf installation? Installing 2 fans (albeit they were both exhaust) did nothing ultimately to lower the cpu temp, since I got 64c either way. My motherboard temp during all this time from what I recall didn't exceed 36c. So it really sounds like the problem lies in the heatsink/fan/thermal compound area, not general air circulation. If I had 1 intake, 1 exhaust, plus my dual fan psu, would this REALLY lower my temps that much (5c or more?). I want to find the true culprit here, not just find ways around the real problem. Thanks for any help.

20c?!

yes, I think this points to a bad HSF install, or just a bad HSF to begin with. Try remounting with the ceramique, and examine the base of the heatsink. If it has a really rough finish, it might be worth running some 400, 600, 800, 1200 and/or higher sandpaper over it until it's nice and smooth. Also make sure your CPU fan is moving a good amount of air, and the heatsink is rated high enough for your chip.

20c delta = crappy hsf, case cooling, or both.

What heatsink are you running in what case with what fans where?

I personally get a 2C delta (on water), but I used to get 8C with a mid range air setup.

I'm using the stock Intel Pentium 4 hsf. I bought this computer so I don't know how well the hsf area was put together. Right now I have a dual fan psu, one exhaust fan below that, and one exhaust fan at the bottom of the front of the case (yeah, I know it should be intake, but the wires won't reach long enough to make it intake, and I don't have an extender right now).

Personally I would prefer no fan on the front bezel as opposed to exhaust fan. Exhaust in front and back are counter-productive. It sohuld be fairly easy to extend the fan wire if you wanted to. The heatsink could deifnitely be the culprit here, especially if you're overclocking.

coolcpu2 said:

I'm using the stock Intel Pentium 4 hsf. I bought this computer so I don't know how well the hsf area was put together. Right now I have a dual fan psu, one exhaust fan below that, and one exhaust fan at the bottom of the front of the case (yeah, I know it should be intake, but the wires won't reach long enough to make it intake, and I don't have an extender right now).

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3 exhausts, no intakes. LOL

Definately remove the bottom front fan (if you can't turn it around and make it an intake fan). That will significantly improve your case airflow and have a beneficial impact on your case temps.

If you bought the computer with this fan set-up, I would certainly question the heatsink installation. You may want to reinstall the HSF with a fresh application of Arctic Silver.

Regards,
GoodKarma

Unplugged the bottom front fan, don't think it's making much difference. Fairly certain it's a problem with the hsf area, not general air circulation. With the cpu at 64c, the mobo only got to like 36c. Not exactly cool, but I don't think that's the problem. No, the people who put my computer together didn't put in that fan setup. I just have no way to put an intake fan in the front without getting some adapter, or a different fan, which I'm looking into.

crappy cooler...i must've screwed up my V9 because i was getting the same problem so i figured i'd try a speeze falcon rock tp (and use the SF2 from the V9) and i only get a 10C difference between idle/load on F@H and 11C on P95...

Your cpu temp is only 18c over your mobo temp at load with the stock cooler, I wouldn't consider that terrible or an indication of a bad mounting.

What temperature does that mobo sensor report? Is that a chipset temp or just a spot on your motherboard? You could easily shave atleast 6 degrees celcius off your load temperature by improveing your case cooling if 36C is your approximate case temperature.

You need to give the case an intake. One exhaust fan and one passive intake will kick the junk out of two exhaust fans with no intake every day of the week. If you don't mind hacking up your case you can make a passive intake in the bottom of your case and leave the fans the way they are. Just make an opening to let some air in that case - cool air has to come from somewhere and with no intakes there is virtually zero flow in your case.

I don't see any reason to look elsewhere for problems - your case airflow needs fixed. Improving your case airflow should improve temps considerably.

Welcome to the forums!

Thanks for the advice IMOG, but the difference between the mobo temp (dunno where it's taken from) and the cpu temp at load (max I've seen is 64c) is not 18c, but rather 28c. 64-28=36. I don't think this is a general circulation problem. But, I did order some fans so I will be able to see what a front intake fan will do to help.

coolcpu2 said:

Thanks for the advice IMOG, but the difference between the mobo temp (dunno where it's taken from) and the cpu temp at load (max I've seen is 64c) is not 18c, but rather 28c. 64-28=36. I don't think this is a general circulation problem. But, I did order some fans so I will be able to see what a front intake fan will do to help.

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Holy jeesh... it's been a long summer, good thing I'm going back to school soon. I've met my calculus requirements already, but perhaps I should look into a remedial mathematics course. I hope Nihili doesn't see this, I feel ashamed.

This could very well be a mounting problem with that much of a temperature difference. You should remove your heatsink, clean, reapply grease, and remount. While you have the heatsink removed, if the base of your heatsink is badly damaged you should seriously consider a lapping - if it has mild marks, lapping could still improve temps by a few degrees.

You are right, this is probably not a general circulation problem as long as your second temperature reading is correct (If you want to find out where that reading is coming from, just read your motherboard manual). It is good that you have plans on installing an intake though too. Without any way for cool air to enter, your case is choking. Since you already have two fans plus the PSU exhausting, be sure that your intake has room to pull air from outside and push air into the case - it needs to be working efficiently.

Just out of curiousity, does removing the side from your case effect your temps and by what amount?

Thanks for the response. I don't see off hand where in the manual the mobo temp sensor info is unfortunately. Maybe I'll check out the temps with the side of the case off tomorrow. Ambient temp does make a difference, right now at idle I'm at 38c cpu and 31c mobo. That cpu temp would probably go up to around 58c right now if I ran the Sandra burn-in. I don't know a lot about this lapping, what would I need and about what would it cost me? Right now, I'm just planning on following the directions to install Ceramique, when it gets here. I've never done anything like this before so I hope I do it right and don't mess anything up or make things worse. Heck, if I could just get the cpu to max at 59c that would be acceptable to me, but I'd like 55c or less. I'm not even overclocking, I shouldn't be getting these high temps I saw no instability even at 64c, but man, psychologically, why would I want to run just 6c below "max die temp"? I don't know exactly when thermal throttling takes over but I'd hate to have to rely on that.

coolcpu2 said:

I don't know exactly when thermal throttling takes over but I'd hate to have to rely on that.

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Hope it is an Intel.

But really, your problem is easy to fix. Just do what everybody has said. You obviously have poor air flow no matter what your temps say, no specification exists for computers where there is no intake fan. Please read THIS and all will be answered. ALso, it is nothing to see a computer built from a retailer to be at around 50c-55c. THose types of temps scare me, I hate when it gets above 36c full load.

Solution, punch a hole in the case for an intake fan, replace that OEM heatsink with a real one. Good Luck!!

Nod, it's a P4. I'm getting a fan for intake, getting Ceramique, I just need to wait for the orders to arrive.

I got the guts to take off my hsf. What I found seems odd to me. What does the stock Pentium 4 thermal pad look like? What I encountered was a sooty area, and on the bottom of the heatsink was a metallic strip. Is this the thermal pad? Didn't seem very "paddy", seemed like some metallic strip that was just left on the bottom of the heatsink. Anyway. I don't have the ceramique yet and I need some high quality isopropyl alcohol before I do much more.

Sounds like they forgot to remove the protective covering from the thermal pad when they installed the HSF...Can you tell if the "metallic strip" can be removed from the pad?? If it looks like you can strip it off of there, do so and give it a try that way to see if your temps improve...May just be a manufacturers snafu that can easily be remedied...

Keep us posted on your progress...and watch those temps!!!

That's the thing, I saw no pad at all. What I saw was a sooty area at the bottom of the heatsink, and just a metallic strip on the bottom of the heatsink which I removed. Is it possible that they had no thermal pad on it at all?

Or the POS was just bad. Mabey it melted or something. I have seen those pads do some pretty strange things, they are all crap!!!!