Pentium M
Introduced in March 2003, the Pentium M is a seventh-generation 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 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 Pro). It is optimised for power efficiency, a vital characteristic for extending notebook computer battery life. Running with very low average power consumption and much less 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 (400 MHz FSB, no HT)).
Essentially, 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, and twice as much cache: 64k primary (as compared to the PIII's 32k, the P4's 8k or the Athlon's 128k) and 1MB secondary (as compared with the 256k or 512k in the PIII, P4 and Athlon). The usually power-hungry secondary cache uses an innovative access method to avoid switching on any parts of it not actually 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.
Intel launched its improved Pentium M, formerly known as "Dothan," on May 10, 2004. "Dothan" Pentium M processors are the first Intel processors to be identified using a "processor number" rather than a clockspeed rating, and are known as Pentium M 735, 745, and 755 (running at 1.70, 1.80, and 2.00 GHz respectively). These 700 series Pentium M processors retain the same basic design as the original Pentium M, but are manufactured on a 90nm process. Die size, at 84 mm2, remains in the same neighborhood as the original Pentium M although the 700 series contains ~140 million transistors, most of which make up the massive 2MB cache. TDP is also down to 21 Watts (from 24.5 Watts in Banias), but dissipation at lower clockspeeds has increased. However, tests conducted by third party hardware review sites show that Banias and Dothan equipped computers have roughly the same battery life.
On May 9, 2004, Intel announced that future desktop and server CPUs would be based on the Pentium M design instead of their NetBurst architecture. The signifigance of this announcement is a fundamental change in the evolution of microprocessors.
CPUs in 2005 and beyond.
CPU performance is primarily determined by a combination of 2 factors: architecture and clock speed. The architecture of a CPU lays the base for how a CPU will perform. This includes the design of the CPU itself and optimizations such as MMX, SSE, and SSE2, these factors together form an approximation known as IPC or Instructions Per Clock. Clock speed is simply the number of clock cycles a given CPU runs each second, usually in the familiar MHz and GHz. Overall performance from these figures is derived through the simplified formula of IPC * Clockspeed = approximate performance.
The trends in Intel's CPUs with the Pentium 4 line followed a design favoring performance derived through the simplification of the design (longer burst pipeline aka Netburst architecture) to allow much higher clock speed (more GHz). The result is that clock per clock Intel's CPUs were slower than others (ie. Pentium 3 & AMD Athlon) but able to run higher clock speeds helping to compensate in overall performance.
As development furthered however, Intel found that increasing clock speed dramatically enough to increase performance at the level they desired began to produce an unacceptable level of heat, causing issues with reliability/stability. This led to the scrapping of the codename Tejas core (sucessor to the current Prescott) and the switch to development of the Pentium M core (really an enhanced Pentium 3) basically moving them back before the Pentium 4 was even released. The current project of both AMD and Intel is to use 2 CPUs on a single die, effectively having a 2-CPU computer with just one chip (although performance might suffer a little compared to the usual dual-processor solutions due the fact that both CPUs still share the same memory).
