Introduced in March 2003, the Pentium M is an x86 architecture microprocessor designed and manufactured by Intel. The processor was originally designed for use in laptop personal computers. It was codenamed "Banias" before its introduction. The codenames of the Pentium M are all locations in Israel, the location of the Pentium M design team.

The Pentium M represents a radical departure for Intel, as it is not a low-power version of the desktop-oriented Pentium 4, but instead a heavily modified version of the Pentium III design (itself a modified form of the Pentium II). It is optimised for power efficiency, a vital characteristic for extending notebook computer battery life. Running with very low average power consumption and much lower heat output than desktop processors, the Pentium M runs at a lower clock speed than the contemporary Pentium 4 desktop processor series, but with similar performance (e.g. a 1.6 GHz Pentium M can typically attain or exceed the performance of a 2.4 GHz Northwood Pentium 4 (FSB400, no Hyper-Threading Technology)).

The Pentium M couples the execution core of the Pentium III with a Pentium 4 compatible bus interface, an improved instruction decoding/issuing front end, improved branch prediction, SSE,SSE2 and (from Yonah onwards) SSE3 support, and a larger cache. The usually power-hungry secondary cache uses an innovative access method to avoid switching on any parts of it not being accessed. Other power saving methods include dynamically variable clock frequency and core voltage, allowing the Pentium M to run slowly (typically 600 MHz) when the system is idle in order to conserve energy.

The processor forms part of the Intel Centrino platform.

Although this CPU was intended strictly as a mobile processor at first, desktop motherboards were manufactured for it in limited quantities beginning in late 2004, and Intel began tweaking the core for the possible release of a desktop version around the same time. An adapter has been developed by ASUS to allow the use of Pentium M processors in selected ASUS motherboards designed for socket 478 Pentium 4 processors.

Banias

The first Pentium M was identified by the codename Banias. It was manufactured on a 0.13 micrometre process, was released at frequencies from 1.3-1.7 GHz, and had 1 MB L2 cache (compared to 256 KB or 512 KB in the contemporary P4 and Athlon processors). It did not support the Hyperthreading enhancement, that was just becoming available on the Pentium 4, but most analysts believed that the processor design would not realize a performance gain with the addition of Hyperthreading due to a number of architectural differences between the P6 and Netburst cores.

Dothan

Intel launched its improved Pentium M, formerly known as Dothan, on May 10, 2004. Dothan Pentium M processors are among the first Intel processors to be identified using a "processor number" rather than a clockspeed rating, and the mainstream versions are known as Pentium M 715 (1.5 GHz), 725 (1.6 GHz), 735 (1.7 GHz), 745 (1.8 GHz), 755 (2.0 GHz), and 765 (2.1 GHz).

The processor line had models running at 1.0-2.13 GHz as of February 2005. The models with lower frequencies were either low voltage or ultra-low voltage CPUs designed for even better battery life and reduced heat output. The 718 (1.3 GHz) and 738 (1.4 GHz) models are low-voltage, while the 723 (1.0 GHz) and 733 (1.1 GHz) models are ultra-low voltage.

These 700 series Pentium M processors retain the same basic design as the original Pentium M, but are manufactured on a 90 nm process. Die size, at 84 mm², remains in the same neighborhood as the original Pentium M, even though the 700 series contains ~140 million transistors, most of which make up the massive 2 MB cache. TDP is also down to 21 watts (from 24.5 watts in Banias), though power use at lower clockspeeds has increased slightly. However, tests conducted by third party hardware review sites show that Banias and Dothan equipped notebooks have roughly equivalent battery life.

Revisions of the Dothan core released in Q1 2005 support a 533 MHz front side bus and NX bit.

Yonah

The next incarnation of the Pentium M, codenamed Yonah, taped out in mid-September 2004 and is due to sample late 2005 and ship in volume in Q1 2006. Yonah is a dual-core design targeted for manufacturing on a 65 nm process, and it will be Intel's first dual-core processor designed from scratch (as opposed to just duplicating existing processor cores onto a single die). Yonah is expected to include 2 MB of L2 (possibly 4 MB) and to target 2.5 GHz at launch (possibly 2.67 GHz), with a front side bus of 667 MHz. The cores are believed to be based on the Banias microarchitecture, extended with SSE3, EM64T, the Vanderpool (VT) virtualization technology, but most likely without Hyper-Threading. The processor is also expected to have the capability to disable one core to conserve power. There will also be a single core version.

Merom

Intel expects to launch the Merom core in late 2006. Merom will support the EM64T instruction set, and Intel plans to use the Merom core as a basis for a new desktop core, Conroe.