You’ve seen the ads on TV, in newspapers, and across giant flying moon blimps. Bennett Ring tells you what the hell it is, and if you really need it.
Every man and his PC building dog are jumping on board the mobile PC bus to cash in on this high-growth rate sector. Wireless computing is almost as hot -- according to Intel, more than 50% of laptops sold in 2003 will include Wireless adaptors. These two trends appear to be the driving force behind Intel's new Centrino platform, which was originally known as Banias. But what the hell is it, if it's not just a CPU or motherboard chipset?
The actual word Centrino is yet another Intel-ism like Pentium and Celeron, that has no real world meaning, but we think it actually means 'massive marketing campaign to stitch up the mobile PC/wireless market without anyone catching on'. It also happens to have the ponciest logo we've ever seen.
For a laptop to get 'Centrino' certification, it must have three Intel components. First up is the new Pentium-M CPU, easily the most exciting part of the package. You'll also need to include a motherboard based around Intel's new 855GM or 855PM chipset. Finally, the laptop will need Intel's PRO/Wireless 2100 802.11b network. Once you have all three together in one box, the right to slap a Centrino sticker on it is yours. Intel is testing many of the world's public wireless hotspots and whacking up huge Centrino posters if the hotspot is configured correctly for Centrino laptops.
The theory is that this will help make wireless more accessible to the masses, eliminating any incompatibilities between the user's machine and the access point. Isn't that just grand of Intel? Obviously it believes the rest of the market doesn't have a clue about building wireless networks and PCs that work well together. Intel also thinks this campaign will help drive the rollout of wireless networking – with Intel at the helm of course. It must be noted that manufacturers can include all three components separately, minus the fluffy Centrino logo. Let's take a look at these components in a little more detail, and continue the bitching about the whole concept of Centrino towards the end of the article.
ABOVE: The new Centrino Hot Spot signs in action.
Intel 855 motherboard chipset Available in two flavours, the GM (with integrated graphics) and the PM (without). Think of this as a revised 845 chipset… except it isn't. Sure, it has the same feature set, but it has been redesigned with power saving as the foremost concern. As a result it's not quite as speedy as the i845 chipset, as some of the power saving features incur added latency, but the difference isn't massive. It also uses a power-optimised variant of the ICH4, known as the ICH4-M (aka the Southbridge), which supports six USB1.1/2.0 ports, integrated LAN, and AC'97 sound. The front side bus is identical to the original Pentium 4's, being a quad pumped 64-bit 100MHz bus. Intel claims the integrated graphics of the i855GM are twice as fast as its Extreme Graphics chipset – unfortunately we couldn't prove or disprove this claim, as it's not just a simple matter of replacing the video card, as it would be in a desktop machine.
ABOVE: The gory details of Centrino, from left to right; Intel's PRO/Wireless 2100, the Pentium-M and the i855 chipset.
Intel PRO/Wireless 2100 Centrino currently only supports the 802.11b Wireless protocol, thanks to this wireless network adaptor. There's nothing remarkable about it, apart from the fact that for a laptop to be Centrino certified, it must use Intel's own adaptor. It's obvious Intel wants to move into being a supplier of wireless networking gear in a big way, but we find it quite ridiculous that other, more experienced manufacturers of wireless gear are totally excluded from the Centrino concept. Intel is planning on integrating the wireless functionality into the MCH (aka the Northbridge) that will support both 802.11b/g. When that happens, manufacturers won't need to install a separate wireless network adaptor, which is a very nice feature. However, the fact manufacturers are forced to use Intel's wireless adaptor in the meantime is something that many companies aren't going to be too pleased about. If you step on too many toes Mr Intel, you're going to get burnt as your feathers melt. Or something like that.
Pentium-M CPUFinally we get to the extremely cool feature of Centrino: the fantabulous Pentium-M. Designed by the same team responsible for Intel's aborted Timnah CPU, the Pentium-M is a very interesting CPU. Here's why.
For starters, it has a massive 1MB L2 cache. That's right, an entire megabyte – until now this amount of cache has been limited to the ultra badarse processors such as the Xeon.
The benefits of this are obvious: just take a look at the performance boost the Northwood P4 received when it doubled its L2 cache to 512KB. The L2 cache of a CPU is one of the most power hungry sections of a CPU, so Intel's engineers had to figure out a way to lower its thirst for juice. They ended up using a technique that is up to four times as power efficient as a normal L2 cache, helping to keep the Pentium-M battery friendly. Like most of the power saving compromises introduced in Centrino's components, this incurred a latency hit, but the massive amount of cache balanced this out; its size also allowed the the Pentium-M to contain 77 million transistors, all on a 0.13 micron process.
Intel won't tell anyone just how long the pipeline is on the Pentium-M, other than to say that it's longer than a PIII pipeline, but shorter than the P4's. This helped to increase the frequency of the Pentium-M without turning it into the power whore that is the Pentium 4. However, a longer pipeline also leads to a greater penalty hit when branch mis-predictions occur (when the CPU guesses the wrong answer to an operation or instruction), as there is more to be flushed out of the pipeline when things go pear shaped.
So Intel developed an improved branch predictor it claims is 20% more accurate than the branch predictor on the PIII, helping to lower the occurrence of pipeline flushes.
Another revolutionary feature of the Pentium-M is known as Micro-Ops fusion. Damn this sounds cool. This technique bundles decoded instructions together and sends them all down the pipeline at once, making more efficient use of the pipeline. This can lead to a sizeable decrease in the amount of power used by the processor. Again, it's a little slower than the standard method of sending one decoded instruction down at a time, but it's worth it if you get better battery life.
While many of these power saving steps lead to slower performance, the other techniques such as the large cache and better branch prediction make this a CPU with a higher IPC (Instructions Per Clock) than the Pentium 4. In fact, it even has a better IPC rate than the PIII – nice work Intel!
This leaves Intel in a bit of a sticky situation. While the Pentium 4 was partially designed to hel
Issue: 133 | February, 2012