Pentium M

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 based on the Pentium Pro core design). 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 (FSB 400 (100 MHz quad-pumped)), 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 Intel has marketed the Pentium M exclusively as a mobile product, several motherboard manufacturers(Aopen,DFI,etc) developed and shipped Pentium M compatible desktop boards in late 2004. An adapter(CT-479) has also 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 using FSB 400 (100 MHz quad-pumped), and had a 1 MB L2 cache.

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 FSB 533 (133 MHz quad-pumped) and NX bit.

Yonah

The next incarnation of the Pentium M, codenamed Yonah, taped out in mid-September 2004 and is due to ship in late 2005 for volume introduction in early 2006. Yonah is a dual-core design targeted for manufacturing on a 65 nm process, and will be Intel's first dual-core processor designed from scratch.

Yonah consists of two cores based on the Banias/Dothan microarchitecture, a 2MB L2 cache shared by both cores, and an arbiter bus that controls L2 cache and FSB access. Floating point performance has been drastically improved through the addition of SSE3 instructions and improvements to SSE and SSE2 implementations. Yonah also includes Vanderpool (VT) virtualization technology and the ability to disable one core to conserve power.

Yonah is expected to launch at 2.13 GHz with a Front side bus speed of 667 MHz (166 MHz quad-pumped). A single core version will be marketed under the Celeron M brand.

In early 2005, rumors began circulating that Intel was considering tweaking the Yonah core for a possible release on the desktop. Confidential Intel presentations also indicate that Intel intends to release a version of Yonah, codenamed Sossaman, for blade servers.

Merom

Intel expects to launch the Merom core in the second half of 2006. Merom will support the EM64T instruction set, and will serve as the basis for a new desktop core, Conroe.