Pentium® M

The Pentium M processor was the first design to emerge from Intel's Israel design centre and was conceived when it became apparent that the Pentium 4's Netburst architecture was rapidly becoming too hot and power hungry for anything other than desktop replacement laptops, and marked Intel's first movements towards the 'performance per watt' dynamic which has become so prevalent recently.

Banias

To get a head start in development the first generation Pentium M, the Banias, borrowed the Tualatin execution core and coupled them with an improved front end, Pentium 4 compatible front side bus interface, improved branch predictors and a larger, 1MiB, L2 cache.
Every measure possible was taken to maintain the CPU's power efficiency, the L2 cache design was vastly different to that of previous CPU's and allowed cache accesses to be made without having to power up the entire 1MiB of cache and Speedstep 3 was also introduced which brought several enhancements such as variable core voltages (down to just 0.844v in Ultra-Low Voltage models), intermediate clock speeds between the maximum and minimum clock speeds depending on load, and new deeper sleep C-states for when the CPU was idle.

Despite this focus on low power consumption the Banias core also managed to be an impressive performer, in some benchmarks a Pentium M 1.6GHz could outperform a Pentium 4 2.4GHz while consuming less than half the power, and when it was launched on March 12th 2003 quickly became the mobile processor of choice, particularly as part of the Centrino platform which became synonymous with long battery life and wireless networking.

Initially the Banias ran at between 1.3 and 1.6GHz, with a 1.7GHz part added in June of the same year, all with a TDP of 6-24.5w (6w being the lowest power state). Low (1.1 and 1.2GHz) and Ultra Low (900, 1000MHz) voltage parts followed in September with TDP's of 6-12w and 4-7w respectively. Finally a year later 1.3GHz LV and 1.1GHz ULV parts were added.

Dothan

The Dothan was landed on May 10th 2004 and saw the Pentium M move to 90nm. The underlying design of the processor remained the same but the L2 cache was doubled to 2MiB, meaning that despite the process shrink the actual size of the die remained roughly the same. Full load power consumption dropped to 21w however lowest sleep state consumption increased slightly to 7.5w, possibly owing to having to power more L2 cache or an increase in gate leakage (although this was nowhere near as major an issue as in the far higher clocked Netburst based Prescott's).

At launch only 1.7, 1.8 and 2GHz parts were released, with Banias remaining to fill in the lower end of the range but by October the Dothan range spanned from 1.4 to 2.1GHz. Dothan's however were not marketed by clock speed and formed the 700-series of CPU's.
As with Banias Low Voltage and Ultra Low Voltage models followed, with the ULV's consuming as little as 3-5w of power at up to 1.3GHz.

In January 2005 the second generation Centrino platform, codenamed Sonoma, launched with a new revision of the Dothan core.
The front side bus was increased to 533MHz (4 x 133) and XD bit support was added, a feature that eventually trickled down to the rest of the Dothan range over time.
Interestingly the TDP of the CPU also increased, up to 10.8-27w, presumably to account for the extra overall power consumption of the system with the increased FSB speed.
Finally in July 2005 a 2.26GHz part was added.

Overview

The success of the Pentium M range started marked the beginning of the end for the Netburst architecture. Although it was intended only for laptop use motherboard manufacturers began making enthusiast orientated desktop boards, and Asus produced an adaptor that allowed it to be fitted to there popular Socket 478 motherboards, and it quickly gained a cult following, overclocking strongly, taking world records in some benchmarks where Prescott was left floundering against the competition and doing so at a fraction of the power consumption of anything other contemporary CPU's.

Archived Pentium® M 1.3GHz

Banias core engineering sample. Part of a complete, working, CRB platform validation kit with ATX motherboard, DC-DC power adaptor daughter card and PCI to mini-PCI adaptor with 2200BG wireless card. Pulled from a lab bin.

Archived Pentium® M 1.6GHz

Banias core retail stepping, pulled from my Thinkpad T40 when upgrading.

Archived Pentium® M 735A (1.7GHz)

Dothan core, purchased second hand on eBay to replace the Banias 1.6GHz in my Thinkpad.