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January 15, 2009

The Intel Atom processor phenomenon

Frustrated with the small display and insufficient battery life of your mobile or handheld computer? Is it also too big and just not quick enough? And you can't stand a fan coming on and the thing getting so hot you can barely touch it? Welcome to the world of mobile computing where optimizing mutually exclusive goals is the order of the day. As a result, manufacturers of mobile gear are fighting a never-ending struggle to find the best compromise -- and it is always a compromise -- between size, weight, usability, performance and battery life. The screen should be large enough to be useful. Size and weight should be such as to render the device as mobile as possible. Performance should at least be adequate. And the battery must last long enough to get the job done. Long battery life either means a big battery or a device that doesn't use much power, and the latter is often preferable. Displays use a lot of power, especially with the backlight up high, but you simply need to see what you're doing and so display size may be a given.

Which gets us to the processor. There was a time when processors cost next to nothing and the mere thought of needing to cool them with a big fan would have been preposterous. When I bought my first IBM PC in 1981, it cost US$4,000, in 1981 dollars. It was powered by a 4.77MHz Intel 8088 processor that you could be at any electronics store for about six dollars (the folks who proclaim that ALL electronics components have become so much cheaper obviously weren't around in 1981). Intel managed to parlay the processor business into a near monopoly, with Microsoft and Intel going lock-step in a mutually advantageous game of creating ever more resource intensive software. Microsoft made Windows bigger and bigger, and Intel delivered the processors needed to run it. That's what got us to a point where software needs minutes to boot, and the processor, chipset and graphics card all need big fans for cooling. Oh, and while the cost of computers has come way down, the cost of Intel processors has gone way, way up. A big new one can cost a thousand dollars, and even more modest ones approach the cost of low-end notebooks. A halfway decent Core 2 Duo costs more than a little Acer Aspire One netbook.

How can Acer, and everyone else who makes small, inexpensive computers do it? Increasingly by using the Intel Atom processor, which is smaller, uses less power, and costs relatively little. Why did Intel do it? Because they found themselves in a predicament. Microsoft increasingly insists that every computer must run Windows proper. The 1990s experiment with Pocket PCs is essentially over. By insisting that small platforms had to be compatible with Windows, yet making sure they didn't get powerful enough to be a threat to the Windows business, Microsoft successfully kept the wings of mobile devices clipped, to the extent where they eventually disappeared as viable platforms. Just the other day I came across a press release from a major manufacturer of rugged handheld computers that said its customers increasingly demanded full Windows even on handheld devices. And that gets us right back to the Atom processor.

Now cost isn't as much of a factor in the vertical marketplace as it is in the consumer market. I am not saying cost doesn't matter, but a market where a device may cost US$4,000 has a bit more leeway than one where customers expect US$800 pricing. What does matter, though, is size, weight and battery life. So what Intel did with the Atom processors is essentially remove the processor as a major power consumption factor. What do I mean by that? Well, an average Core 2 Duo desktop processor uses around 65 watts, a mobile version about 35 watts. There are chips that use considerably more or a bit less, but those are the rough numbers.

Now how do we know how much power a processor uses? After all, Intel sells them using a weird nomenclature that, unlike light bulbs that have a watt rating, seems unrelated to performance. Instead, Intel usually provides what they call the "Thermal Design Power," or TDP. TDP is described as "The maximum amount of heat which a thermal solution must be able to dissipate from the processor so that the processor will operate under normal operating conditions." There's a good deal of debate as to what TDP actually means and how it relates to real world power consumption of a processor. But for the sake of the argument, let's assume we're talking watt-hours and the processor is in a battery-powered computer. We can easily compute the battery's watt-hours by multiplying volt and amp ratings. A powerful notebook computer battery may provide 75 watt-hour, just enough to run a typical desktop processor for an hour (and that's without the power needed for the display and everything else in the notebook). A frugal notebook processor with a TDP of 25 watts would run three hours, and that sounds about right (in the real world, the processor uses power conservation modes most of the time, but you have to add in the power used by all the other computer components).

Now what does an Atom processor use? Between 0.6 and 4 watts. There are two different families of Atom chips, one geared towards mobile Internet devices (MIDs) and one towards netbooks and other low-cost PCs. The most popular chip in mobile computing is probably the 1.6GHz Atom N270, which has a TDP of 2.5 watts. That's the chip you find in almost all current (early 2009) netbooks and in many embedded components. Why two families? Because MIDs and PCs have different feature requirements. MIDs are usually multimedia-oriented and power consumption is totally crucial because the devices are so small. Netbooks and similar generally rely more on compatibility and standard PC interfaces (like SATA).

So where do the Atom processors fit in as far as power consumption goes? Well, 2.5 watts is sensationally low compared to just about anything else available. The generally unloved Intel Core Solo uses about 5.5 watts in its ultra-low power version (U1300/1400/1500), the Core 2 Solo (U2100/2200) about the same, the mobile Core 2 Duos between 10 watts (U7500) and 45 watts (Q9100/9300). So the most popular Atom processor uses less than half the power of a Core Solo and only a small fraction of that of the Core 2 Duo chips.

Now keep in mind that processors need corresponding chipsets, and those use power, too. Intel designed a super-efficient chipset to go with the MID-oriented Z5xx series of Atom chips that was once codenamed Silverthorne. That chipset, the "Poulsbo System Controller Hub," can do high definition video decoding and other neat stuff required in consumer multimedia devices, and it only uses about 2.3 watts. However, it does not support serial ATA and some other essentials, which rules it out for many computing applications. The N2x0 series of Atom chips uses the i945GSE, which is a slowed-down version of an older Intel chipset, the i945. That's good as far as compatibility goes, but there is no high-def decoding and 3D performance is low. The i945GSE uses about 5.5 watts, so overall consumption of the N270 and the chipset is still only about 8 watts, but it's not exactly a state-of-the-art solution.

How about performance? This is where it gets a bit complicated because overall "performance" of a computer depends not only on the CPU, but also the chipset, the memory, the hard disk or SSD, overall system configuration and -- very important -- the OS platform and software loaded. That said, we run fairly extensive benchmarks on all systems that come to our lab, and so far we've found that an average Atom N270 device scores roughly one third of that of a 2.5GHz Core 2 Duo T9400, about 30% less than that of a 1.2GHz Core Duo U2500, about the same as a 1.2GHz Intel Core Solo U1400, and about 50% better than that of a 1GHz Celeron M 373. So we're talking decent, but certainly not blazing speed.

As far as architecture goes, the Atom is an interesting mix of old and new technologies. It's definitely state-of-the=art in terms of miniaturization, using Intel's hafnium-based high-k manufacturing. That is a fancy terminology describing the use of different conductor materials to make even tinier transistors possible. The architecture of the chips is less advanced. There's only a single core, though Intel uses the old HyperThreading technology known from as far back as the Pentium 4. There are also advanced new power savings technologies.

Overall, the Atom is certainly an interesting marketing phenomenon. At this point, everyone is clambering to get onboard the Atom bandwagon, and somehow Intel managed to stay clear of the nuclear power connotation though one would expect that from a name like "Atom." Intel, though, stresses the hafnium-based manufacturing process, and hafnium's primary use is in control rods in nuclear power plants, so that may be the "Atom" connection. In any case, even with the sub-optimal chipset situation, the lack of some features, and only moderate performance, Atom is hot. And in the new Intel world order of massively expensive processors, Atom is cheap, too, with prices of well under US$100 depending on the type and version. I've seen $44 for the N270 mentioned, and about the same for some of the low-end Z5x0 chips plus their Poulsbo chipset. Oh, and if you wonder what the difference is between the N270 and the 230, there is a N270 and a 230 that run at the same speed, the N270 is for mobile applications whereas the 230 uses a bit more power (4 watts) and is used with a considerably more power-hungry version of the of the i945 chipset, making the Atom 230 more suitable for desktop use.

As usual, there are numerous expert opinions out there, and the overall consensus seems to be that, for now, the Atoms just represent Intel's first step into the small form factor embedded and a MID market that is pretty much dominated by ARM-based designs.

With Intel's resources and marketing savvy, Atom as a "low power" processor platform may well be here to stay. As is, they are off to an amazingly good start.

For much more information on the Silverthorne platform, check Intel's Intel Atom processor Z5xx Series.

Posted by conradb212 at January 15, 2009 04:42 PM

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