ThrottleWatch is a utility for detecting and reporting the CPU throttling activity in Pentium 4, Xeon, and Pentium M processors.

The amount of heat a CPU produces varies according to the processing load. In situations of high sustained load (such as performance benchmarks, etc...), a CPU may produce more heat than the cooling mechanism is capable of removing, and reach a high enough internal temperature to trigger throttling.

ThrottleWatch monitors and graphically displays both the CPU load and any throttling that occurs.

When ThrottleWatch is minimized, an icon is added to the system tray area of the Taskbar. The color of the icon changes when throttling is detected.

Types of CPU throttling:

TM1: "Thermal Monitoring 1" throttling is a feature of Pentium 4, P4 Xeon, Celeron ("Northwood" or "Prescott" cores), and Pentium M CPUs. TM1 throttling does not reduce the CPU clock speed - it inserts idle cycles into the instruction pipeline to reduce the processing load on the CPU, which in turn lowers the CPU temperature.

TM2: "Thermal Monitoring 2" throttling is a superset of TM1 and is used on LGA-775 versions of the Pentium 4 and Celeron processors and also on the Pentium M series of processors. TM2 reduces processor temperature by lowering the CPU clock multiplier, and thereby the processor core speed.