Intel Centrino mobile computer platform

The first generation Centrino platform (codenamed Montara) was announced in March 2003. The trio of systems that comprise Centrino focus on battery life and the integration of wireless LAN technology. Only systems that include all three components:

  • a Pentium-M processor
  • the Intel 855 chipset family
  • an Intel Pro/Wireless LAN adapter.

are allowed to use the Centrino brand.

The Intel Pentium-M processor – previously codenamed Banias – should not to be confused with the earlier Pentium 4-M. Manufactured on Intel’s 0.13-micron process technology and with a die size of 100mm2, the new CPU combines some of the best features of earlier designs to produce a new microarchitecture capable of delivering high performance with reduced power consumption.

Like the Pentium III-M, the Pentium-M adopts the same design principal of performing more processor instructions per tick of the system clock. It does this without generating too much heat and can run at low voltages. In addition, it also supports the Pentium 4-M’s quad-pumped 400MHz FSB and support for both vSIMD and SIMD2 instructions to further boost performance. Since power consumption is directly proportional to clock speed, it is not surprising that a Pentium-M runs at lower clock than a Pentium 4-M, the new CPU being initially available is speeds from 1.3GHz to 1.6GHz. At the time of its launch, Intel claimed that a 1.6GHz Pentium-M offered comparable performance to a 2.4GHz Pentium 4-M at 50% less battery drain.

In addition to the new core, the processor’s Level 1 cache has been increased to 32KB from the Pentium III-M’s 16KB and the Level 2 cache is a full 1MB. However, to reduce power consumption when running on battery power, the chip only powers up the amount of L1 cache it actually needs – estimated by Intel to be 1/32 of the full cache size on average.

The new chip also introduces further refinements in Intel’s established SpeedStep technology, which dynamically reduces processor speed and voltage as the situation allows. The Pentium-M’s more compartmentalized processor allows finer control over shutting down the parts that aren’t needed and reduces the voltage before the frequency slowly enough for the CPU to be able to continue what it’s doing whilst this is happening.

Designed in tandem with the Pentium-M processor, the Intel 855 chipset has a lower core voltage in comparison to previous generations of memory controller hubs and utilises innovative design features to reduce memory interface power during system idle conditions. Design enhancements such as increased burst length size, timing improvements and shorter refresh cycles also contribute to improved performance.

The 855 chipset’s features include:

  • a 400MHz (100MHz x four) system bus offers a peak bandwidth of 3.2GBps
  • DDR memory channels offering a peak bandwidth of 2.1GBps, and
  • an AGP 4x interface allowing graphics controllers access to main memory at over 1GBps.

and the new ICH4-M Southbridge offers standard support for:

  • Ultra ATA/100
  • 10/100BaseTX Ethernet
  • AC97 audio
  • PC Card
  • Modem
  • USB 2.

The chipset comes in two forms, the 855PM and the 855GM, the latter including integrated graphics.

The third and final Centrino component is the Intel PRO/Wireless adapter. When details of Banias were first revealed in 2002, the expectation was for the wireless networking support to be hardwired into the motherboard as part of the chipset. In fact, Wi-Fi has been implemented as a mini-PCI card and slot. This is a more sensible arrangement, since it allows more scope for upgrades of a rapidly developing technology.

Indeed, it was not long before the benefit of the revised strategy were seen. With the work on wireless standards progressing more quickly than had been expected, Intel revised its plans for upgrading Centrino’s original 802.11b part to accommodate other wireless standards. By mid-2003, the schedule was to have introduced a dual-band 802.11b/802.11a adapter by the third quarter and to have bundled support for 802.11g by the end of the year.

Also scheduled for the end of the year is for the Centrino processor manufacturing process to move from 0.13-micron to 0.09-micron. With the chip available in both FCPGA and FCBGA packages, these low voltage CPUs offer the prospect of high-powered, wireless-networked, ultra-portable notebooks in the not too distant future.