Thermal throttling

Every modern CPU and GPU carries an on-die temperature limit, commonly around 95-105 °C for a CPU junction and 83-90 °C for a GPU core. When a sensor reaches that limit the chip drops frequency and voltage within microseconds. Nothing is broken when this happens; the mechanism is protective and designed-in. What matters is whether it happens at the temperature you expected and how far the clock falls.

Throttling is the single most common reason a machine feels fast for the first ten seconds of a workload and mediocre afterwards. A short benchmark run finishes before the heat has propagated from the die into the heatsink, so it reports the boost clock. A long export, compile, or game session runs almost entirely in the throttled state. This is why peak numbers and sustained numbers can differ by 30% or more on the same laptop.

SystemCheck cannot read your temperature sensors. No browser can. What it can do is measure the consequence. The 60-second sustained multi-core CPU load records throughput continuously, and the decay figure in your report is the drop from the early window to the late window. A large decay on a load that never changes is the fingerprint of throttling, whether the cause is heat, a power limit, or a current limit.

If you need the actual temperature that triggered it, pair SystemCheck's decay measurement with HWiNFO64, Core Temp, or your motherboard vendor's monitoring utility on Windows, or `sensors` on Linux. SystemCheck tells you that performance is falling and by how much; a hardware monitor tells you which limit caused it.