[Honeywell PTM7950 Phase Change Thermal Pads/Sheets] Application, Tips, and Results

[Michael_Wu]

@Usernames

It might be possible to test that by starting with CPU sitting above 45 so PCM is melted (better still if the iGPU also). That should eliminate the phase change from the equation, if you fancy the challenge hehe. If the phase change is significant it should be fairly easy to tell with changes in temperature profile alone.

I dug into this a bit and below are my findings.

All of this was run from Windows 10 on High Performance profile (so idle temps were a bit higher). Ambient temps around 77F.

First run:
Starting at 43-44C ThrottleStop chip sensor (I forgot to check but I’m pretty sure all cores were below 45C). Running Prime95’s Small torture test, the first vertical line on the graph shows 86C @ 12.3W:

The next vertical line shows 89C at 58.8W:

Afterwards, it steadily rises to a max of 100C @ 59.5W.
(Note at lower idle temps, I can hit 60W+).

Second run:
I let the laptop cool a bit to 47-48C (ThrottleStop’s chip sensor and I forgot to check if all CPU core temps were above 45C. I think they were, but not sure.). Then I reran Prime95’s Small torture test. First vertical line shows 95C at 52.4W:

Afterwards it does still steadily rises to 100C. But the duration is much shorter (probably since it started at a higher 95C).

Third run:
I let it cool down a bit from the second run and then stressed the CPU in short bursts with ThrottleStop’s CPU bench (starting/letting it run for 1-2 seconds), then stopping and making sure all cores are above 45C. You can see where I did this in the graph:

Then running Prime95’s Small torture test, the first vertical line shows 95C @ 56.0W:

Afterwards, a short duration steady rise to 100C.

Fourth run:
I let the laptop cool to 42-44C (ThrottleStop’s chip sensor) and this time ensured all cores were under 45C (ranged from 35-42C).

Prime95’s Small torture test, first vertical line 82C at 10.1W.

Next vertical line 90C at 58.5W.

Afterwards, a significantly longer duration rise to 100C.

In conclusion, it seems that even with all cores above 45C, the steadily-rising-to-100C behavior remains. I also reread this post which has data on CPU change on stock vs. Kryonaut vs. Conductonaut liquid metal. It seems that all of them have the steadily-rising-behavior as well, though the duration to 100C is longer with “better” paste. So I don’t think the phase change behavior of PTM7950 changes things too much – I could be wrong/missing something though.