by March 4, 2003 0 comments

In the desktop world, processor speed is an important criterion for selecting a computer, but while going for a notebook, people also look for other factors like battery life and form factor. Now days they have also started looking for wireless LAN capabilities. 

Now there is a product, or rather a combination of products, which promises to address all these needs of mobile users at one go. Intel is bringing out a new Mobile PC platform called Centrino (read brand). This has three components, a Pentium M processor, Intel 855 chipset and a Intel pro/wireless network connection. A notebook manufacturer can use any of the three components separately, but can use the new Centrino logo, only if they use all the three components in the laptop. This is the first time that Intel has shifted focus from the processor or the chipset to a combination, a “whole platform.”

The Centrino platform has the Intel Pentium M processor (codenamed Banias earlier) and is to be offered in three versions–standard 1.6 GHz, low voltage 1.1 GHz and ultra-low voltage 900 MHz. This new CPU does not have a close relative in Intel’s desktop family of CPUs (Pentium III and Pentium 4) like the other mobile processors Pentium III-M and Pentium 4-M. That is, it is designed exclusively for mobile systems and is not a desktop CPU adaptation.

The processor is made using 0.13-micron technology with 77 million transistors, which is more than the Pentium 4, and 1 MB of L2 cache. In a processor each and every processor cycle uses up power. In a notebook, this can lead to faster draining of the battery. In order to overcome this, the Pentium M CPU has a comparatively higher IPC (instructions per cycle) rate. This means it can do more work in fewer clock cycles. 

Other features of this new CPU include Power Optimized cache, Power Optimized Processor Bus, Advanced Branch prediction, Micro-Op Fusion technology, Dedicated Stack Manager, Streaming SIMD Extensions (SSE) 2, and Enhanced SpeedStep technology. Power optimization in the System bus and cache is achieved through turning off parts of the FSB that are not being currently used. 

The eight-way associative L2-cache of Banias is divided into four power quadrants per way. The quadrants that are not being accessed at the moment can be ‘’shut off’’ and put to sleep. Also the L2 cache gate power leakage is reduced. Micro—op fusion is the sending of decoded instructions down the processor pipeline in bundles to improve efficiency. These are separated just before being sent to the execution units. Power usage is also reduced because of a more efficient use of the pipeline. Banias also has a dedicated stack manager to manage stack pointers and other stack-related data, which improves efficiency and thus power consumption is optimized. 

The processor overall has a power optimized logic design which results in lower power consumption and thus lower heat dissipation. Lower heat dissipation allows for smaller and thinner and lighter notebooks and batteries than before. All these features together are supposed to ensure that the average power consumption of the processor is less than 1W, while still delivering good performance, thus extending the available power on a standard battery.

To complement all these energy saving technologies, Centrino gives the manufacturer the option of using one of two motherboard chipsets–the 855PM (ODEM) or the 855GM (Montana). The difference between the tw is that the 855PM links to a dedicated GPU (graphics processing unit; on a separate video card) via an AGP 4x port, while the 855GM comes with integrated 3-D graphics. Both support DDR memory, have a mobile optimized memory controller and communicate with the Pentium-M processor over the 400MHz (100 MHz Quad pumped) low power system bus.

On the wireless front, Intel is initially offering a 802.11b WLAN mini PCI card called Calexico, but is soon expected to launch a dual 802.11a/b card, supporting both 802.11a and 802.11b standards, the a version being faster than the b version.

With Centrino the aim is to improve performance combined with mobility and not just raw performance as in the case with desktop processors, which are going on and on in the clock speed race with latest offerings being at 3.06 GHz. 

With Centrino, Intel seems to accept that clock speed is not everything, and that similar performance can be provided with better design on slower clock speeds also.

Ankit Khare

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