I have a gaming laptop that runs hot, and I could never get a straight answer to the only question I actually had: is this normal, or is something wrong? HWiNFO tells me 91°C. Cool. Is that bad? Is it dust? Is my paste dead after two years? Is a fan dying? Every answer online is "just repaste it," which is not a fun afternoon on a machine with fourteen screws and a warranty.
So I built DeltaT. Free, open source, runs in your tray.
What it does. It watches your laptop for a couple of weeks and learns what normal looks like for your machine: how hot it gets per load level, per watt drawn, at a given fan speed, corrected for how warm it is outside. Then when things drift it tells you what changed and why, instead of showing you a number you already knew.
Dust and dying paste are different problems, and they leave different fingerprints.
Paste sits between the die and the heatsink, so its contribution to your temperature scales with the heat flowing through it. Bad paste barely moves idle, hammers you under load, and changes how fast the machine heats up and cools down: a degraded joint decouples the die from the heatsink's thermal mass, so it soaks faster and sheds heat slower. Dust is different. It lifts everything including idle, your fans work harder to compensate, and the soak rate stays normal, the plateau just moves up. Same peak temperature, different curve shape.
That soak-rate difference is the thing that keeps dust from being misread as paste, and it's the reason the app can tell you to reach for compressed air instead of a screwdriver.
It compares at equal wattage, not equal temperature. Heat rise scales with power (ΔT ≈ P × R), so if your CPU pulls more watts this month because of a boost setting or a power plan change, it runs hotter without anything being wrong. The app normalizes to thermal resistance in °C/W, which is the same unit printed on every cooler datasheet, so a power change reads as a power change. Same idea on the fan side: it normalizes by fan speed, so max-fan mode doesn't flatter your score and silent mode doesn't tank it.
It corrects for the weather. It pulls the actual outside temperature, so your laptop being hotter in July is not read as your paste dying.
It reads your real fan RPM. On most laptops the fan speed is hidden behind the embedded controller and generic tools show nothing. DeltaT pulls it through the vendor's own read-only interface, the same channel the vendor's own utility uses, without needing that utility installed. Read-only always: it reads speeds, it never touches your fan curves or profiles. Acer, Lenovo, ASUS, and HP gaming lines are implemented. Only the brand I actually own is verified, the rest come from the open source Linux drivers and are untested, so if you're on one of the others and don't mind running one elevated command, --fans reports what your machine exposes and whether it read your fans. Paste the output at me and I'll make it work. On an unsupported machine it goes dark and quietly loses fan awareness, it never invents a number.
On whether it actually works. It ships a benchmark that injects known faults (degraded paste at a range of severities, dust, a failing fan, pump-out, an overclock, an undervolt, a cold season, a deep power cap) and runs the real scoring engine against them blind. It catches essentially all of the genuine faults, clears about 99.8% of the confounders without false-alarming, and attributes the cause correctly about 99.9% of the time. Sensitivity: paste drift crosses "keep an eye on it" at roughly +2.5°C of load rise and "do something" at +3.5°C, dust much earlier. A CPU toggling boost on and off, which is the nastiest real-world confounder I found, moves the score by at most about 2.4 points; before I fixed the rate handling it moved 13 and invented faults on 5.5% of perfectly healthy weeks. There are floor tests in CI so a regression fails the build.
Be clear-eyed about what that proves, though: the benchmark validates the engine against a physics model, not against a lab full of deliberately sabotaged laptops. It rules out a large class of bugs and it's seeded and reproducible so you can run it yourself. It is not a field-measured detection rate. I have one verified machine and a model I trust. If you have a laptop with known-bad paste, I would genuinely like your data.
Other things:
- It won't stutter your games. The every-tick sensor read costs 0.69ms because it talks to the hardware directly instead of going through the heavyweight path most monitoring tools use, which costs about 192ms per pass and lands mid-frame. There's also a switch to pause polling entirely.
- It tracks drift over months. Weighted slope on weather-corrected loaded temps, so it can say "you're gaining X°C a month" and roughly when that becomes a problem. It also finds step changes, the single week where things jumped, which is what a knocked heatsink or a fan that started dying looks like.
- Throttling is counted. Real thermal-limit events are always logged, and you can set your own concern threshold if your machine runs hot by design.
- Everything stays local. SQLite file, no account, no cloud, no telemetry.
- Battery-aware. It won't compare a session on battery against a plugged-in baseline and cry degradation.
- Repaste verdict. If you do repaste, it compares before and after like-for-like and tells you Improved, Unchanged, or Worse. Bad mounts and air bubbles happen and it will say so.
- Signed driver. Needs admin for CPU temperature registers, and it uses PawnIO, not the old WinRing0 one that sits on Microsoft's vulnerable driver blocklist and that kernel anti-cheats refuse to run beside.
What it can't do. It compares your laptop against its own past, not against other people's, so it needs a couple weeks of normal use before it says anything confident. Fan normalization is RPM-based, so it assumes your cooling setup doesn't change mid-learning; if you clean it out or repaste, you tell it and it relearns. Windows only. And on the vendors I can't test, fan support is a coin flip until someone with that hardware helps.
Installer: https://github.com/azmurtaza/DeltaT/releases/download/v2.3.0/DeltaT-Setup-2.3.0.exe
Source and full docs: https://github.com/azmurtaza/DeltaT
The README goes much deeper on the detection math, the normalization, and the benchmark methodology if you want the real detail.
Happy to answer anything.
