CPU temp jumps. GPU temp OK t42

[irus]

okay after i applied as5 on the gpu and cpu the cpu temp seems to jump up to 80-85 while watching a simple youtube video. at the same time the gpu temp hovers around 70. is this normal?

should i try out the video pad material on the cpu, its probably not making good contact with the heatsink?

edit: idle temp of cpu is 45 and gpu 50 ambient temp being 28-30

[richk]

Too hot. AS5 will transfer heat better than a pad. I assume you have a long fan. They come with a pad., Did you remove the pad? Padte should not be under the pad. Is it possible you used too much paste on the CPU? A thin layer works MUCH better than too much.

[irus]

Too hot. AS5 will transfer heat better than a pad. I assume you have a long fan. They come with a pad., Did you remove the pad? Padte should not be under the pad. Is it possible you used too much paste on the CPU? A thin layer works MUCH better than too much.

thats right its a long fan. the pad was scraped off while switching motherboards. the gpu and heatsink copper have as5 between them only.

i applied as5 using the plastic bag method using very little of it. but i did apply it on both the heatsink and on the cpu/gpu. what would be good temps on t4x? both at idle and under load? and how fast does the temp move under load? so that i get some idea of normal performance.

[irus]

so is this a case of too much as5 on the cpu or could it be the heatsink is not sitting flly flat on the cpu? just need to be a bit more sure before opening it up! ideas welcome.

[n2rj]

Could be the heatsink not sitting fully on the CPU. I have a 2.1GHz Dothan in my T40 and even after an hour of 100% cpu load it doesn't cross 72-75 degrees.

[poshgeordie]

To add to the previous answers.

If the heatsink came with a pad in the GPU area then use a pad with no heatsink compound on it.
If it didn't come with a pad then you need to see if one is supposed to be fitted. I think we have discussed this elsewhere, but basically if there's a slight gap between the top of the GPU and the bottom of the heatsink then you need to use a pad of the correct thickness (refer to your previous post where we discussed this). Don't try to bridge the gap with compound since it won't work and the GPU will overheat.

On the CPU there should be no pad and the thinnest of thin coatings of heatsink compound.
As has been said already too much could well cause a rise in temperatures. Remember the heatsink compound is there to fill in the miniscule imperfections in the mating CPU and heatsink surfaces, so the thinner the better.

Good luck and let us know how it goes.

[irus]

Could be the heatsink not sitting fully on the CPU. I have a 2.1GHz Dothan in my T40 and even after an hour of 100% cpu load it doesn't cross 72-75 degrees.

hmm i used prim95 to do a 100% cpu load test.
in 3 mins it reached from 37 (switch on temp) to 75
and in another 3 mins reached 80!

gpu went up from 41 to 66 in the 6 mins.

wondering whats the normal performance? say for 10 mins under 100% load like this.

[irus]

i noticed the jump in temp of cpu is not only upwards but downwards as well.. from 64 to 51 in 1 second! whats happening here?

[sjthinkpader]

The heatsink is doing its job. The quick change in temperature is with the number of I/O and internal switching going on.

CMOS logic shorts to ground momentarily as it switches. Because the moment is very short, it was a huge improvements as compared to NMOS and PMOS. Everything changed to CMOS in the late '80s. But as chips pack more and more circuits inside, buses got wider and wider, data got transferred not once but twice on every clock cycle; they generated more and more heat nevertheless.

The Dothan CPU uses 90nm design rule, packs a lot of parallel buses internally and access memory in double cycles externally. So it heats up quickly and cools off quickly. The heatsink is designed to remove a lot of heat too. So it can take down the temperature once the processing stops.

[irus]

The heatsink is doing its job. The quick change in temperature is with the number of I/O and internal switching going on....

interesting info! one question, while applying as5 is it proper to apply it on both heatsink and gpu/cpu or either heatsink or the cpu/gpu? method is the plastic bag/using the tiniest grain of as5.

[sjthinkpader]

I only apply thermal compound to one side, on top of the chip. Actually use Dow Corning 111 equivalent.

[irus]

i got some time today to pull apart the tpad again. and i noticed gpu heatsink corner closest to the harddisk was 0.5 mm higher than the rest and not contacting the gpu properly

so the breaker grozier pliers went to work and bent the heatsink in shape. then i read on as5 website that cpus with mirror finish need to have just a translucent bit of as5 on them. i tried that but it was a failure.

i put as5 on cpu and gpu and heatsink alike using a plastic bag. and the results are much more stable now.

ambient temp 30 C

cpu/gpu

46 / 51 idle
48 / 54 watching a video on vlc

using prime95

0 minutes 46 /51
3 minutes 70 / 60
6 minutes 75 /64 stable and not climbing

back to idle temperature in 4 minutes.

no more temperature jumps.
i guess the temps will be lower in windows xp than windows 7 that im on right now.

[JoshuaR]

Mm, I've got those temp jumps too. I replaced my fan a few weeks ago and first applied the thermal grease (brand: Stars and then Chinese characters that I can't read) on the top of the CPU using the plastic bag method. I turned on my computer and was quite happy to see everything pop up to normal, but then boop black screen and shut down. I assumed my new fan wasn't doing its job. I took everything apart again, pulled out the new fan assembly, and reapplied the grease, both on top of the CPU and on the fan assembly for good measure. This time I just put "dots" of grease that would theoretically get smushed out and cover all of the surface area, probably with a thicker layer than with the plastic bag method. I crossed my fingers, tried again, and... success! Then the next day, just using my computer normally, boop black screen and shut down. Uh oh. I then installed tpfancontrol just to see what the hell was going on (if it was a heat issue). The temps show that the comp is basically always under 60 for normal stuff but then jumps up to 95 or so when doing anything from Youtube videos to using Google Maps (this one isn't quite as bad a load, but still something). I always pause the video or slow my activity AND usually make sure I switch tpfancontrol to fan speed 7 or 64 just for good measure. So far my computer hasn't forced anymore shut downs on me, but I still worry that I will never be able to watch movies again. (Unless I do need to go for the "third time's a charm" guess on the fan installation.)

[irus]

hi josh from what you describe it seems like the contact between the heatsink and cpu/gpu is not good. how i located the bad contact point was i let the comp cool down by switching it off for 5 minutes. then i pulled out the fan. the area with dotty (or where u can see the white area of the chip and spotty as5 on it) as5 is where the contact is good and the area where as5 is smooth and thick and where the white part of gpu chip is not visible is where the contact is bad. then i used pliers to pull down the corner of the heatsink. next time i let it run the videos etc without putting the screws back on the keyboard (put the screws back in the fan for sure). i was satisfied with the temps. so i pulled out the fan after 5 mins of cool off period and saw that entire gpu contact area was dotty this time and no place had smooth as5. which meant it was all making good contact.

the plastic bag method works great on the gpu but the cpu needs a sligtly thicker layer. in both cases applying as5 both on heatsink and gpu/cpu works well. i used the plastic bag method too and left just a little extra as5 on the heatsink for the cpu this worked. no more temp jumps either going up or coming down.

[JoshuaR]

Thanks, I'll take a look at that.

[visionviper]

Thanks, I'll take a look at that.

I'd also check to make sure the fan is working properly to begin with. When temperatures are that high your fan should probably be spinning away at it's highest setting. If it doesn't sound like you have a small RC helicopter in your laptop your fan might be the problem.

Though I would have to lean to a heatsink contact problem just because the temperatures are so high for what the processor is doing.

[JoshuaR]

Yeah, it's definitely working. It's quieter than I remember my old fan, but that's mostly because my old fan did the buzzing (people thought I was boiling a pot of tea) sound and then some sort of screeching rattle before I replaced it. I definitely hear the fan volume go up nice and high when it's at speed 7 or 64.

Thanks for letting me know that I'm not imagining something and that there is something fishy going on!