Tcase vs Tjunction, Laptop heat problem

Justin_126 · Oct 28, 2016

Hi All,

My Spectre X360 is suffering from throttling on and off which appears to be related to some sort of tcase cooling issue.

My tcase is always AT LEAST 22C higher than tjunction which appears to be causing throttling which is hugely frustrating.

I was getting the following when idling (averages)
SSD 43C
tcase: 68C
tjunction: 44C

I cleaned out the fans with compressed air and I get this when idling.
SSD 41C
Tcase: 67C
Tjunction 37C

Under load before clean
SSD: 47C
Tcase 91C
Tjunction: 66C

Under load after clean
SSD: 45C
Tcase 86C
Tjunction: 60C

What is making tjunction so stubbornly high and how can I reduce it? Even cleaning the fans made little ifference to tcase?

Now the former is far too high but the later seems about right

Ecky · Oct 28, 2016

Tcase is a measurement of the temperature of the top of the heatspreader. There is no Tcase spec for notebook CPUs because there is no integrated heatspreader on the CPU, it's bare die.

What sort of throttling behavior are you seeing? What are you using to load it? What are you using to measure temps?

Justin_126 · Oct 28, 2016

What I am calling tcase is the following:
Temp1 in Speedfan
Package Temp in Intel Extreme Tuning
TZ01 (motherboard) in HW Monitor

All of these tempretures are always in line with each other so they are clearly measuing the same thing.

What I am using for tjunction is
Core Temp in HW Monitor
Core Temp in Speedfan.

For example if I look in Speedfan now I have
HDD - 39C
Temp1 64C
Core 0 38C
Core 1 37C

When temp1 hits 80C I see throttling of the CPU to 1.2ghz until temp1 goes down to 65c and then gradually the CPU goes back up to 2.2ghz, before the pattern repeats.

The biggest issue is that if the CPU runs at full clock speed, once the load starts hitting more than 60%, the Temp1 / package temp hits 80C, even though the cores may only be say 52C, throttling kicks in and the CPU gets downclocked.

The issue I then have is that the more CPU power I need, the less I get. I know that sounds stupid, but it's true. When the CPU is under light load, it gets 2.2ghz, when I really need that power the most the CPU power drops, so I tend to get either low CPU usage and high clock, or high CPU and low clock.

I'm not convinced that the fan logic is right either,, which doesn't help.

Ecky · Oct 28, 2016

This is a "design feature" often seen in thin PCs and mobile devices like phones, and the premise of "turbo". CPUs are allowed to run at much higher speeds than the enclosure they're in can run continuously, for brief periods, to make it feel like a much faster PC for light usage. After all, why limit the CPU to 1.2ghz if that's all the enclosure can disspiate continuously, when you could briefly run as high as 2.2ghz?

Ultimately you're limited by what the chassis can dissipate continuously under heavy loads, and it's unlikely there's anything you can do about it. This is the tradeoff with small/thin PCs.

What are you using to generate load? Is this real-world usage like games/encoding/rendering, or are you using an artificial torture-tester like Prime95 or IETU's stress testing?

Justin_126 · Oct 28, 2016

And that is what I would agree with previously, however the performance is so bad now that it has literally dropped off a cliff in the last few weeks to the point where the machine is far slower than it has been before and this throttling is a very recent phenomenon, which doesn't make sense why the sudden change. I have messed with virtually every BIOS and power setting I can find and ran every benchmark going and I still cannot find why this problem came on and

I've looked at a friends Spectre (same model number, built around the same time, same CPU, ram and SSD) and they do not have this issue and are running same BIOS version.Their heat profile is very different. Their temp1 in Speedfan is much cooler with their coretemp higher and their case hasn't been cleaned out either and their motherboard thermal temp is much lower,

So whatever that temp1 is in my machine in speedfan and the package temp being much higher and motherboard temp being much higher has to be the cause. What I don't understand is what is causing the heat. if my CPU cores are running much hotter, why is the package and the MB running much hoitter.

I'm simulating loads with Intel's own stress testing software. The results I get are in line with much lower end CPUs, again must be caused by the throttling, same test on my friends machine, identical setup, typical for the I5-5200u.

Ecky · Oct 28, 2016

I assume you're seeing the same sort of slowness during typical usage too?

This machine is most likely non-serviceable, and it may be that there has been a failure inside - maybe a heatpipe that cools some motherboard component (VRMs?) has come loose and is no longer making good contact. Or, possibly, blowing compressed air into it damaged one of the fans; I generally don't advise people do this for this very reason, and frequently replaced broken fans at the shop I worked in until recently.

Justin_126 · Oct 28, 2016

I'd be surprised if it was a fan issue, because this behaviour happened even before I used compressed air on it. I used compressed air to try and see if it would help, and the problem hasn't really changed since then.

The fans only seem to respond to the core temp being high though, that is what is strange. They only kick in when that hits 60C and the machine cools very fast and they are very powerful and working well. The core temp is well within normal ranges and is always very cool so it's reasonable why the fans would not kick in.

The root of this issue seems to be the package temp (in Intel tools) Temp 1 (speedfan) and the Motherboard temp being always much warmer than the core temperature (which appears to be what triggers the fans). Now to test this I ran some tests on another spectre, which did not suffer these issues.

The strange thing with the other Spectre is that it's SSD and core Temps all ran hotter than on my machine, yet the motherboard temp and the package/temp1 on speedfan were all much lower. Which brings me back to the original point. What is that tempreture and why is it so out of kilter with every other temp in my machine?

For example this is my machine vs his at idle
Data - Mine - His
Idle MB - 62C - 45C
Core0 - 41C - 48C
Temp 1 - 63C - 45c
Pack Temp - 62C - 45C
SSD - 41C - 46C
(I assume Temp1 in speedfan and Idle MB in HW monitor package temp in intel tools are same thing)

How can I have a situation where my cores are running 7c cooler than another spectre yet the board and some other unknown temp are running 17C warmer than his board? How can the motherboard be 21C hotter than the CPU core in my machine and his the CPU is 3C hotter than the motherboard? Doesn't make sense.

Justin_126 · Oct 28, 2016

Just saw motherboard hit 92c with CPU at 61c, something very wrong here.

I've ordered a new fan and some thermal paste, changed BIOS to fan always on and using third party software to disable turboboost for the time being until I can work this out before I fry something.

Does anyone know if it's possible to work out where the sensor for the MB tempreture is on the 360? If I could it might help me narrow down what is getting that hot...

On thoughts of it, probably not the best cooling design
http://www.laptopultra.com/guide/wp-content/uploads/2015/05/HP-Spectre-Pro-X360-Disassembly-4-600x400.jpg

There's a vent on the side but the fan is pushing air up onto solid metal, since the grills are not directly above the fan. Could it be that because of this heat is being pushed away from the CPU, onto the rest of the machine, which is why the machine is hot and the CPU is cool?

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