Glossary/Thermal/Thermal headroom
Thermal headroom
Thermal headroom is the gap between a component's current temperature and its throttle point, which determines how long it can sustain boost clocks.
Also known as temperature headroom, thermal margin
Measured by SystemCheck
Part of the four-stage run: a 60-second sustained CPU load reporting throughput, decay and consistency; a memory stage reporting bandwidth and latency; a GPU raster load at a fixed resolution reporting frame rate, pacing and decay; and a path tracer reporting samples per second. The paragraphs below say which metric carries this term.
Headroom is what boost algorithms spend. A chip 30 °C below its limit will boost aggressively; one 3 °C below it will not. This makes headroom, not absolute temperature, the quantity that governs how a machine behaves at any moment.
Headroom shrinks over the course of a session as the case, cooler, and ambient air all warm. It is why the same machine performs differently at the start of a work session and three hours in, and why a benchmark result depends on whether you ran it cold.
SystemCheck cannot report headroom in degrees. It measures the behavioural consequence: how much throughput falls across a sustained run. A shallow decay means you had headroom to spare through the run; a steep one means you exhausted it. For a degrees-based reading, use a hardware monitor alongside.
Headroom also explains why the same test gives different answers depending on when you run it. A machine that has just woken from sleep starts with its full margin and boosts hard for longer; one that has been rendering for an hour starts with almost none. To compare two runs fairly, start both from the same state, and if the question is how the machine behaves late in a long session, use a run long enough to spend the margin, such as the deep run with its hot re-test.
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