TM2, or "Thermal Monitoring 2", is a throttling control method used on LGA 775 versions of the Pentium 4, Pentium D

Pentium D

The Pentium D brand refers to two series of desktop dual-core 64-bit x86-64 microprocessors with the NetBurst microarchitecture manufactured by Intel. Each CPU comprised two dies, each containing a single core, residing next to each other on a multi-chip module package. The brand's first processor,...

 and Celeron processors and also on the Pentium M

Pentium M

The Pentium M brand refers to a family of mobile single-core x86 microprocessors introduced in March 2003 , and forming a part of the Intel Carmel notebook platform under the then new Centrino brand...

 series of processors. TM2 reduces processor temperature by lowering the CPU clock multiplier

CPU multiplier

In computing, the clock multiplier measures the ratio of an internal CPU clock rate to the externally supplied clock. A CPU with a 10x multiplier will thus see 10 internal cycles for every external clock cycle...

, and thereby the processor core speed. (In comparison, TM1 insert an idle cycle to CPU for thermal control, without decreasing multipliers).