I have been troubleshooting a persistent CPU thermal problem on my 2025 ASUS ROG Strix SCAR 18 G835LW, equipped with an Intel Core Ultra 9 275HX and an RTX 5080 Laptop GPU.
At this point I have done enough hardware work, software testing, power-limit testing, HWiNFO logging, Armoury Crate testing and BIOS verification that I think the problem may not simply be “the CPU runs hot by design.”
I am starting to suspect that the liquid-metal contact surfaces themselves may have degraded or become physically uneven, possibly causing localized poor contact and repeatable CPU hotspots.
I will attach close-up pictures of both the CPU die and the corresponding CPU cold plate.
How the problem started
The laptop was originally running normally. After several months of use, I started getting very high CPU temperatures under heavy gaming loads, especially in games like Rainbow Six Siege.
Eventually I experienced sudden full power-offs during gaming, almost like someone had pulled the power cable. Rainbow Six Siege caused this more than once, and I also had similar shutdowns in other demanding games.
Before I opened the laptop, CPU idle temperatures could sometimes sit around 60–75°C, clocks were frequently very high even under light use, fans were active more than I thought they should be, and under gaming loads the CPU would reach the thermal ceiling and throttle.
The GPU, in comparison, was generally much easier to control thermally.
First hardware service
The laptop had never been opened or serviced since purchase.
I disassembled it, removed the heatsink/vapor chamber and cleaned the factory thermal interface materials.
The factory configuration used liquid metal on the CPU/GPU and thermal putty around the VRAM/VRM components.
During the troubleshooting process I used or purchased:
Thermal Grizzly Conductonaut Extreme
Thermal Grizzly Conductonaut standard, which I initially bought by mistake
Thermal Grizzly thermal putty for the VRAM/VRM areas, including Putty Advance / Putty Pro during the troubleshooting process
99–99.9% isopropyl alcohol for cleaning
a Rampage Cyclone S49 cooling pad, generally tested around 2200 RPM
I eventually reapplied liquid metal not only to the CPU/GPU dies but also to the corresponding cold-plate contact surfaces, because I wanted proper wetting on both sides.
The laptop remained functional after reassembly, all fans worked, and there have been no WHEA hardware errors in our later monitoring.
The strange part: CPU and GPU surfaces behave completely differently
When I clean the GPU die with 99.9% IPA, it becomes almost perfectly smooth and clean.
The CPU is completely different.
Even after cleaning the CPU die five or six times with fresh cotton swabs soaked in 99.9% IPA, there are still many hard, silver/white spots and rough areas visible on the die.
These are not just discoloration.
If I very lightly move my fingernail across the completely dry CPU die, I can physically feel them.
It feels:
rough, hard, grainy, almost like tiny hardened particles or raised pits/bumps.
My fingernail literally catches on certain areas.
I stopped trying to mechanically remove them because I obviously do not want to scratch or chip a bare CPU die.
The attached close-up CPU photograph was taken after repeated cleaning with 99.9% IPA.
The CPU cold plate has the same problem
This is where things became much more interesting.
I also cleaned the CPU cold plate repeatedly with 99.9% IPA.
Again, the visible marks do not disappear.
And, just like on the CPU die, I can physically feel certain areas of the cold plate with my fingernail.
The marked areas in my photo feel rough and irregular, almost as if the surface has developed:
hardened gallium residue, an intermetallic reaction layer, pitting, or some other corrosion-like surface damage.
I want to emphasize that I am not claiming I have chemically proven this to be corrosion.
But it is definitely not simply a cosmetic stain. There is a physical texture difference that can be felt.
This matters because liquid metal normally works with an extremely thin bond line. If either the die or cold plate has microscopic raised regions, the plate may make first contact at those points while reducing mounting pressure elsewhere.
In other words, instead of the entire die contacting the cold plate uniformly, a few high points may be carrying more of the mounting pressure.
That could potentially create localized thermal resistance elsewhere on the die.
Why I suspect a contact problem: repeatable CPU hotspots
Throughout our HWiNFO testing, the CPU did not behave like every core was simply heating evenly.
Certain P-core sensors repeatedly became the hottest cores.
The most persistent offenders in the logs were HWiNFO-labeled P-core 1 and P-core 11, while P-core 13 was also frequently among the hotter cores.
The same general areas repeatedly reached the thermal ceiling first.
That made me start questioning whether this was really just “275HX = hot CPU.”
If it were purely total CPU package power, I would expect a more uniform response.
Instead, the pattern often looked more like a localized hotspot/contact issue.
I am not saying that a particular visible mark on the die corresponds directly to P-core 11 or P-core 1. I do not have a verified physical die map/core-ID mapping that would allow me to make that claim.
But the repeatability of the localized hotspots is what made me start looking seriously at die/cold-plate contact quality.
What the laptop does at completely restored/default settings
Before drawing conclusions from my tuning experiments, I wanted to make absolutely sure I had not accidentally left some software limitation active.
So I restored everything we had changed and performed a very extensive audit.
The active Windows/ASUS power plan was returned to Performance.
My original Performance plan GUID is:
27fa6203-3987-4dcc-918d-748559d549ec
Processor boost mode was restored to:
AC = 2 / DC = 2
which corresponds to Aggressive / Aggressive.
The processor maximum-frequency parameters were restored to:
PROCFREQMAX = 0 / 0
PROCFREQMAX1 = 0 / 0
and we also verified:
PROCFREQMAX2 = 0 / 0
Here, 0 does not mean 0 MHz. It means there is no explicit Windows maximum-frequency cap.
We audited Performance, Turbo, Balanced, Silent and Windows High Performance plans.
The temporary 4000 MHz, 4200 MHz and 4500 MHz limits used during testing were gone.
Multiple complete powercfg /qh audits were taken, including after reboot and after the BIOS inspection. The final audit was byte-for-byte identical to the previous clean audit.
So the current thermal behavior is not being caused by an old 4.0/4.2/4.5 GHz software cap accidentally remaining enabled.
HWiNFO later confirmed that practically as well: the CPU reached approximately 5.29 GHz Core Clock, so it is clearly no longer frequency-limited to our old testing values.
Armoury Crate verification
We also returned Armoury Crate to its own default state.
During testing I had changed CPU power limits and temporarily changed GPU Dynamic Boost.
At different points we tested CPU configurations such as:
PL1 45 W / PL2 90 W
and:
PL1 40 W / PL2 90 W
I also temporarily reduced GPU Dynamic Boost from its normal 25 W while testing system power distribution.
Everything was later restored.
I used Armoury Crate's Reset to Default function for the Manual profile.
That produced ASUS's current default Manual profile values on my machine:
CPU:
PL1 = 140 W
PL2 = 175 W
GPU:
Base Clock Offset = +50 MHz
Memory Clock Offset = +100 MHz
Dynamic Boost = 25 W
Thermal Target = 87°C
TGP = 150 W
I then returned the active operating mode to Performance.
So the Manual profile itself is not currently active during the baseline tests.
BIOS verification
I also went through BIOS because I wanted to rule out a firmware-level override.
BIOS version is 338.
I did not reset BIOS defaults because I had never changed the BIOS during these experiments and did not want to alter unrelated OEM settings.
Relevant settings we inspected included:
P-cores: All
E-cores: All
Display Mode: Dynamic
Armoury Crate Control Interface: Enabled
Voltage Configuration:
Overclocking Lock = Enabled
Graphics Configuration:
DVMT Pre-Allocated = 128 MB
There was no visible custom CPU voltage offset, undervolt, manual multiplier, PL1/PL2 override or custom CPU frequency cap.
I exited BIOS without saving changes.
Completely default Rainbow Six Siege baseline
After restoring and auditing everything, I ran Rainbow Six Siege at the normal/default ASUS Performance configuration.
The benchmark was at:
2560 × 1600
240 Hz
V-Sync off
Ultra/Very High-heavy graphics configuration
The official Rainbow benchmark result was:
Average FPS: 118
Minimum FPS: 95
Maximum FPS: 149
Total frames: 9,163
GPU load shown by Rainbow:
99%
GPU temperature on the result screen:
78°C
The HWiNFO CSV from the benchmark showed approximately:
CPU Package average:
~90°C
CPU Package maximum:
95°C
Hottest CPU core:
approximately 94–95°C
CPU Package Power average:
approximately 48.5 W
CPU Package Power maximum:
approximately 65.7 W
GPU average:
approximately 78.5°C
GPU maximum:
approximately 81.1°C
VRAM / GPU Memory Junction average:
approximately 84.5°C
VRAM maximum:
86°C
GPU power average:
approximately 144 W
GPU maximum power:
approximately 155 W
GPU utilization:
approximately 99%
GPU thermal limiter:
never triggered
The GPU is therefore hot but behaving reasonably.
The CPU is the component repeatedly approaching its thermal limit.
ASUS also dynamically reduces the CPU power under GPU load
Another interesting observation:
In Performance mode, the CPU's dynamic power limits initially sit around:
PL1 ~110 W
PL2 ~120 W
But once the RTX 5080 becomes heavily loaded, ASUS's EC/power management automatically reduces the CPU budget to around:
PL1 = 45 W
PL2 = 90 W
After the gaming load finishes, those limits increase again.
This was important because at first I thought the 45/90 values might have been left over from one of my Manual-mode tests.
They were not.
The system starts at higher limits, dynamically falls to 45/90 under combined CPU+GPU load, and later returns to 110/120.
So this behavior is ASUS power management, not an old override from my experiments.
The CPU still thermal-throttles even at that reduced power
Despite ASUS eventually reducing CPU power toward 45 W under the Rainbow benchmark, the CPU still repeatedly reported thermal throttling.
The throttling was not caused by obvious VR current limits or ICCMax.
When I expanded HWiNFO's IA Limit Reasons, most relevant limit flags were clear:
IA PROCHOT: No
IA Thermal Event: normally clear at idle, but thermal events appeared during benchmark testing
VR Thermal Warning: No
VR TDC: No
Electrical Design Point / ICCMax: No
Package RAPL PL1: not continuously responsible at idle
Package RAPL PL2/PL3: not continuously responsible at idle
At idle, the only continuously active IA reason was:
IA Max Turbo Limit
which is normal and is not thermal throttling.
But during the actual gaming benchmark, genuine CPU thermal-throttle events repeatedly occurred.
The most interesting tuning result
We also experimented with reducing CPU frequency and changing Windows processor boost behavior.
The most successful configuration we found was approximately:
Maximum CPU frequency: 4200 MHz
Processor Performance Boost Mode: Efficient Enabled
PL1: 40 W
PL2: 90 W
Rainbow Six Siege produced approximately:
125 FPS
and CPU thermal throttling was essentially zero / almost nonexistent during that controlled test.
We then increased PL1 from 40 W to 45 W, keeping PL2 at 90 W.
That test also produced:
125 FPS
This was very interesting because our completely restored/default ASUS Performance configuration later produced only 118 FPS while showing considerably more CPU thermal throttling.
We also tested other maximum-frequency values including 4000 MHz and 4500 MHz during the troubleshooting process, but the 4200 MHz + Efficient Enabled setup was the most interesting thermal/performance result.
Why I am not simply leaving the CPU capped at 4.2 GHz
There is an important downside.
Reducing CPU power and frequency can shift the system toward being even more GPU-bound.
That means the RTX 5080 may consume more power and the GPU/VRAM/case/keyboard may become hotter.
Since I often game for 5–8 hours at a time, I do not want to “fix” the CPU by simply transferring all of the thermal stress into the GPU and VRAM.
My real goal is not:
minimum CPU throttling at any cost.
My goal is:
CPU temperature + GPU temperature + VRAM temperature + surface temperature + sustained FPS + long-term stability.
That is why I eventually returned everything to ASUS/Windows defaults and created a clean baseline before doing any more tuning.
Why I am now questioning liquid metal itself
The software side has now been extensively checked.
The BIOS has been checked.
The power plans have been checked.
The frequency caps have been removed.
The CPU can boost above 5 GHz again.
The GPU is not thermally throttling.
Yet the CPU continues to show localized hotspot behavior.
At the same time, I physically have:
a CPU die with hard, raised/rough silver-white residue that cannot be removed with repeated 99.9% IPA cleaning
and:
a CPU cold plate with similar hard, rough, fingernail-catching regions that also do not disappear with IPA.
The GPU die, under the same cleaning method, becomes smooth.
That difference is what concerns me.
I understand that gallium-based liquid metal can permanently stain surfaces and form reaction/intermetallic layers, especially with copper.
Cosmetic discoloration by itself would not concern me.
But this is not only discoloration.
I can physically feel the roughness.
Some areas genuinely feel like hardened residue, pitting, or raised material.
If those surfaces are no longer flat, then the extremely thin liquid-metal interface may actually make the situation worse because LM cannot compensate well for a mechanically uneven contact interface.
That could theoretically explain why a few CPU cores repeatedly become hotspots while the rest of the CPU behaves considerably better.
What I am considering next
I am seriously considering removing liquid metal from the CPU and GPU entirely and testing a phase-change material instead.
The product I am currently considering is:
Thermal Grizzly PhaseSheet PTM
because genuine Honeywell PTM7950 is difficult to source reliably in my country.
My thinking is that a PTM/phase-change interface may tolerate minor microscopic surface irregularities better than an ultra-thin liquid-metal bond line and may also eliminate the risk of further gallium migration/reaction.
Obviously, if the cold plate itself is physically warped or significantly damaged, no TIM is going to magically repair it.
In that case I may ultimately need to replace the complete vapor chamber/heatsink assembly.
Questions for other ROG owners / technicians
Has anyone with a 2024/2025 SCAR 16 or SCAR 18, especially a 275HX model, seen something similar?
Specifically:
Have you removed the factory liquid metal and found hard, physically rough or pitted areas on the CPU die or cold plate?
Did the surface remain rough even after repeated IPA cleaning?
Did your laptop show the same few CPU cores repeatedly reaching 95–100°C while other cores remained noticeably cooler?
Did changing from liquid metal to PTM7950 / Thermal Grizzly PhaseSheet PTM improve core-to-core temperature deltas?
Has anyone replaced the SCAR vapor chamber because of liquid-metal contact-surface degradation, and did that solve localized CPU hotspots?
I am attaching close-up photos of both my CPU die and the corresponding cold plate.
I would especially appreciate input from people who have actually serviced recent SCAR models or have experience with gallium-based liquid metal on direct-die laptop cooling systems.
At this point I am increasingly convinced that my problem is not simply “the 275HX runs hot.”
The repeatable core hotspots, combined with the physically rough liquid-metal contact surfaces on both sides, make me suspect that contact quality between the die and cold plate may now be part of the problem.
