The same habits apply to technology. When I say Xeon, you think servers. When I say Athlon 64, you think performance desktops. When I say Centrino, you either think of laptops or a wireless networking hotspot serving Starbucks coffee. Either way, we’ve been conditioned into associating marketing names with certain usage patterns. That’s great for Intel and AMD, who invest plenty of money establishing and maintaining brand recognition, but, like McDonalds’ delicious golden French fries, it isn’t always healthy. So guess what. It’s time to break the habit.
Intel’s Pentium M, one of the fundamental building blocks of the immensely successful mobile Centrino initiative, centers on a micro-architecture tailored for minimal power consumption while still delivering plenty of speed. Until now, it functioned exclusively as a notebook processor, in spaces too confined for the Pentium 4’s heat dissipation specifications. However, motherboard manufacturers DFI and AOpen are repurposing the chip as a desktop alternative with specially designed boards. Why?
For its stratospheric clock speed and inclusive feature set, Intel’s Pentium 4 is in a tough place. It runs incredibly hot, draws a lot of power, and currently lags behind many of AMD’s competing products with regard to performance. On the other hand, Pentium M is almost a polar opposite. It’s highly efficient, consumes minimal power, and even at 2 GHz readily trounces much faster desktop architectures in many benchmarks.
Where might a reseller position a platform like that? The server market would be a good place to start. You can’t run dual Pentium M configurations. However, it’d be a relatively straightforward process to incorporate the Pentium M into a small chassis and deliver a lightweight file or mail server. Now, the processor’s accompanying platform doesn’t support PCI Express, DDR2 memory, or 64-bit memory addressability—some of the most recently discussed server topics—but it does fit into tight spaces and perform well enough for basic serving tasks.
Alternatively, the Pentium M would work well in a home theater setup. Its diminutive thermal output means that the chip only requires a tiny, silent cooling fan. Used in conjunction with a capable graphics card, a Pentium M system handles video decoding, 3D graphics, and media playback without even a hiccup. And again, its small size is ideal for the svelte consumer electronic enclosures currently available.
It might also surprise you that Intel’s Pentium M is an adept gaming processor, too. In fact, direct comparisons to the Pentium 4 and Athlon 64 product families show that the Pentium M is as fast or faster than those high-end desktop chips. Considering the cost of most modern processors, platforms, and peripherals, the Pentium M is a more attractive solution.
INSIDE PENTIUM M
There are actually several characteristics that contribute to the Pentium M’s appeal. Perhaps the most significant is its efficiency, which enables much better performance at 2 GHz than many other processors at higher frequencies. Comparatively, the Pentium 4 “Prescott” core employs a 31-stage pipeline that facilitates much higher clock speeds at the expense of efficiency.
Whereas AMD’s Athlon 64 benefits from an on-die memory controller to keep access latencies remarkably low, all of Intel’s processors go the traditional route with memory controllers built into complementary core logic, resulting in higher latencies and lower memory throughput. Pentium M combats that problem with a large 2MB L2 cache repository, minimizing the effect of higher latencies. Consequentially, the Pentium M picks up a lot of extra performance by including such a massive full-speed cache.
And even though the cache accounts for a good deal of the processor’s 140 million transistors, Intel’s 90nm manufacturing process allows the chip to operate with a maximum TDP (thermal design power) of just 21 watts. That’s down from the 130nm Pentium M’s 24.5 watts and 77 million transistors. More importantly, compare that 21 watt TDP to the Pentium 4 3.46GHz Extreme Edition’s 110 watt specification and it should be clear how much power the Pentium M actually saves.
In fact, the chip runs so cool that it doesn’t require a large heatsink and fan combination. The Pentium M motherboards from DFI and AOpen instead come with tiny aluminum heatsinks and equally minute cooling fans. The lack of sound created by a Pentium M platform in action is welcome after listening to a lab full of Athlon 64 and Pentium 4 test beds, especially reaffirming to the processor’s viability in a home theater environment.
That doesn’t mean that everything about Pentium M comes up roses, though. Intel hasn’t devoted the same resources to improving its mobile lineup as it has for the Pentium 4. Thus, it isn’t surprising that the prime ingredient in serving up Centrino lacks SSE3, HyperThreading, and EMT64, Intel’s 64-bit x86 extensions. For all mobile purposes, Pentium M is still very much modern. However, when it has to contend with the Athlon 64’s inclusive feature set, you may find the architecture coming up a little short.
Adding insult to injury, the Pentium M is a pricey processor. At 2.0GHz, it’s roughly equivalent to the 3.6GHz Pentium 4 in terms of price. But while that might seem like a major drawback, the Pentium M’s ability to serve up comparable performance makes the head-to-head comparison more apropos. THE FIRST MOBILE DESKTOP MOTHERBOARD
The idea of repurposing Intel’s Pentium M for desktop use is still very fresh and only a couple of manufacturers have stepped up to give the concept room to breathe. As previously mentioned, AOpen and DFI are the enterprising volunteers. The respective products from each manufacturer are somewhat similar. AOpen’s looks to be intended more for standard desktop use, though, while DFI’s board also looks to be a solid foundation for a server.
DFI’s 855GME-MGF centers on the geriatric 855GME MCH (memory controller hub), which boasts a—don’t laugh—400MHz front side bus, single-channel DDR333 memory controller, Extreme Graphics 2 engine, and AGP 4x slot. The MCH is paired to Intel’s 6300ESB ICH (I/O controller hub), a derivative of the ICH5 that comes with support for 64-bit PCI-X connectivity. Also standard are four USB 2.0 ports, a pair of ATA-100 controllers, two native Serial ATA ports, AC’97 audio, and a standard PCI 2.2 bus.
Therein lays another of the Pentium M’s shortcomings. After preaching the potential benefits of PCI Express, massive memory throughput, and advanced graphics, the 855GME chipset wields nothing but antiquated technologies. It’s like watching a dogfight between a modern F-22 Raptor and a Vietnam-era F4 Phantom. And almost miraculously, the 855GME keeps pace with newer chipsets with more developed specifications.
DFI goes a step further and augments the chipset with a Gigabit Ethernet controller and an IEEE 1394 Firewire controller. There’s even a single, 64-bit PCI-X slot for a high-bandwidth SCSI card or additional Gigabit Ethernet adapter. The board’s integrated graphics core, while suitable for mundane 2D tasks, isn’t up to delivering any sort of 3D experience. So if you’re interested in crafting a gaming system, use an AGP add-in card instead of relying on the very value-oriented onboard solution. Unfortunately, it isn’t really possible to improve the platform’s memory performance. The best you can do is use one large, low-latency DDR333 module and leave one DIMM slot open for a future upgrade. Bear in mind that while the MCH is fairly outdated, Intel’s 6300ESB ICH is fairly modern and supports RAID 0 or 1 across its Serial ATA ports.
You’d naturally guess that an older feature set would help drop the price of DFI’s 855GME-MGF. However, if AOpen’s i855GMEm-LFS is any indication, you can expect the DFI board to cost between $250 and $300. Granted, that’s an incredibly steep price for DDR333 and AGP 4x, but given the platform’s niche audience, the lofty price tag is at least somewhat understandable. Plus DFI bundles a heatsink and fan with the motherboard in case you happen upon a batch of OEM processors rather the more expensive retail boxed version, which does come with its own cooling solution.
PENTIUM M IN THE FUTURE
Even if the idea of adopting Intel’s Pentium M as a desktop platform doesn’t appeal to you right now, keep an eye on the processor, which is due to receive an improved chipset at some point early in 2005. Codenamed Alviso, the next generation of Centrino will push front side bus speeds to 533MHz, incorporate support for PCI Express, Serial ATA hard drives, high-definition audio, DDR2 memory, and the DirectX 9 integrated GMA 900 graphics core. If it’s a more attractive chipset that you’re wanting, Alviso will be the answer. And if the existing AOpen and DFI Pentium M motherboards sell well, you can expect other manufacturers to join the desktop fray when Alviso is released to the mobile market.
Further down the road, Intel is already planning its first dual-core Pentium M, codenamed Yonah and manufactured at 65nm. It will be accompanied by a chipset called Calistoga, which, Intel recently disclosed at its Developer Forum would, focus on extended battery life and security. Other expected enhancements may include 667MHz memory and Serial ATA II support in addition to the technologies enabled by Alviso. As these platforms start incorporating more advanced technologies, you can bet there will be heightened interest in exploiting their efficiency on the desktop.
IN RETROSPECT
Although you may have never considered the ramifications of adopting Pentium M as the basis for a server or, even more absurd, in a high-end gaming platform, with the right complementary hardware, the processor behind Intel’s Centrino is much more pliable than anyone previously recognized.
Mated to DFI’s latest motherboard, based on the 855GME mobile chipset and equipped with Gigabit Ethernet, Pentium M really shines. The combination’s Achilles heel is its outdated core logic, which doesn’t have any problem doling out performance but fails to affirm some of the other desktop technologies that Intel is pushing with the 925XE chipset, for example. If you and your customers can look past the archaic single-channel memory subsystem and older AGP 4x graphics slot, Pentium M delivers speed comparable to the ultra-pricey Pentium 4 Extreme Edition in many tests.
Alternatively, if you’re more conservative on unproven prospects, hold off on Pentium M for now. But keep your eye on the prize because once Alviso drops, you can expect a lot more excitement surrounding the Pentium M, especially if Intel hasn’t pulled itself out of the lull that currently plagues its Pentium 4.
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