Pentium M

From Freepedia

Introduced in March 2003, the Pentium M is an x86 architecture microprocessor designed and manufactured by Intel and forms part of the Intel Centrino platform. The processor was originally designed for use in laptop personal computers, thus the "M" for mobile. 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.

1 Banias
2 Dothan
3 Yonah & Sossaman
4 Merom
5 External links

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 the performance of a 2.4 GHz Northwood Pentium 4 (400 MHz FSB, 100 MHz quad-pumped) with 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 which are not being accessed. Other power saving methods include dynamically variable clock frequency and core voltage, allowing the Pentium M to throttle clock speed when the system is idle in order to conserve energy. The latest innovation in this department is also the incorporation of the SpeedStep 3 technology which has enhanced sleep stages in comparison to the previous versions of SpeedStep. With this technology, a 1.6 GHz Pentium M can effectively throttle to clock speeds of 600 MHz, 800 MHz, 1000 MHz, 1200 MHz, 1400 MHz and 1600 MHz. The existence of these intermediate clock states allows the CPU to better throttle clock speed as per requirement. Another remarkable feature of the Pentium M is its extremely low power dissipation which varies from as low as 5W when idle to only 27W on full load. This feature is extremely useful to notebook manufacturers as it allows them to bundle the Pentium M into thinner, lighter and smaller notebooks.

Although Intel has marketed the Pentium M exclusively as a mobile product, two motherboard manufacturers (AOpen and DFI) developed and shipped Pentium M compatible desktop boards in late 2004. An adapter, the 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.

Pentium M processors are gaining a lot of attention from the embedded systems industry. The low power consumption of the Pentium M allows the design of fanless and highly miniaturized embedded PCs, such as the Toradex Midget (95x70x15 millimeters). In conjunction with the Intel 915GM Northbridge, which comprises up to four lanes of PCI Express, the Toradex Midget computer module delivers very high data throughput rates of up to 4x2 Gigabits/s.

Banias

The first Pentium M was identified by the codename Banias. It was manufactured on a 130 nanometer process, was released at frequencies from 1.3 to 1.7 GHz using a 400 MHz FSB (100 MHz quad-pumped), and had 1 MB of Level 2 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).

These 700 series Pentium M processors retain the same basic design as the original Pentium M, but are manufactured on a 90 nm process, with twice the secondary cache. 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.

The processor line has models running at clock speeds from 1.0 to 2.26 GHz as of July 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), 738 (1.4 GHz), and 758 (1.5 GHz) models are low-voltage (1.116V) with a TDP of 10W, while the 723 (1.0 GHz), 733 (1.1 GHz), and 753 (1.2 GHz) models are ultra-low voltage (0.940V) with a TDP of 5W.

Revisions of the Dothan core were released in Q1 2005 with the Sonoma chipsets and supported a 533 MHz FSB (133 MHz quad-pumped) and XD (Intel's name for the NX bit). These processors include the 730 (1.6 GHz), 740 (1.73 GHz), 750 (1.86 GHz), 760 (2.0 GHz), and 770 (2.13 GHz). These models all have a TDP of 27W.

In July 2005, Intel released the 780 (2.26 GHz) and the low-voltage 778 (1.60 GHz).

Yonah & Sossaman

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. EM64T (Intel's name for AMD64) will not be available in Yonah.

Yonah is expected to launch at clock speeds up to 2.16 GHz with a 667 MHz FSB (166 MHz quad-pumped). A single core version will also be available, and a cut-down version of that 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. Sossaman will be marketed as Xeon LV and ULV. The only difference between Yonah and Sossaman cores will be the capability of the second to be used in 2-way systems.

Merom

Intel expects to launch the Merom core in the third quarter of 2006. Merom will support the EM64T instruction set and will serve as the mobile version of a new desktop core, codenamed Conroe which is different from the existing Pentium M and Pentium 4 processors. Merom's design, like that of the Pentium M, places emphasis on both high performance and low power consumption, consuming about half of the power consumed by Dothan. Ultra low voltage Merom chips will consume as little as 0.5W of power, enabling ultra portable laptops to have battery lives in the tens of hours.