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How Does Core Temp Work?

The short answer: it asks the processor. Every recent x86 chip from Intel, AMD and VIA contains a digital thermal sensor — usually abbreviated DTS — and Core Temp reads it directly instead of relying on anything the motherboard reports.

The digital thermal sensor

The sensor sits on the die itself, inside each core, next to the circuitry that produces the most heat. Because it is part of the processor, its output is independent of the board the chip is plugged into — the same chip gives comparable readings on any motherboard. That is what the site means when it calls Core Temp motherboard agnostic.

Why this beats a board sensor

A traditional onboard sensor sits in the socket area, some distance from the silicon, and reports one figure for everything. It responds slowly and it averages away exactly the detail you want. The digital sensor updates fast enough to show a spike as it happens and reports per core, so a single busy thread is visible as one hot core rather than a small change in a single number.

What the value actually is

The sensor is designed around the processor's own thermal limit. The chip knows the temperature at which it must protect itself — that is the Tj. Max value Core Temp displays — and the reported temperature is expressed in relation to it. This is why Tj. Max varies from model to model and why a reading is only meaningful next to the limit for that specific processor.

Reading it takes a driver

Sensor registers are not accessible to ordinary applications, so Core Temp installs a small kernel-mode driver to query them. That is the reason the program asks for administrator rights the first time it runs, and the reason a security suite occasionally raises an eyebrow at the installer.

Coverage

Digital thermal sensors are present across the recent x86 range from all three vendors; the supported processor list is the authoritative reference. Very old chips that predate the feature cannot report per-core temperatures, because there is nothing on the die to read.

Passing the data on

Readings are not locked inside the program. Core Temp publishes them through a shared interface that plug-ins and external applications can consume, which is how the desktop gadget and third-party tools display the same values. Developers can find the details on the developer page.