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Analysis: The real scoop on Atom-ARM rivalry

Posted: 07 Mar 2008 ?? ?Print Version ?Bookmark and Share

Keywords:Atom? x86 architecture? processor? ARM core?

Intel Corp.'s Atom is a new architecture that offers Pentium M-class performance within a 2W power envelope packed into a 25mm x 25mm die. These numbers are very small for an x86 processor, and they allow Atom to target embedded applications like mobile Internet devices where the x86 has not been used before.

If you believe the buzz, Atom is so good that it will displace ARM cores as king of the mobile world. Unfortunately, the buzz was extremely confused. Here's what the coverage got wrong, what it got right and what it completely missed.

What they got wrong
Atom will beat ARM because it can run Vista. "They've got to be kidding," said Will Strauss, president of research firm Forward Concepts. Mobile devices will not run Vista. "It's a memory hog and power-consuming hog. Maybe Windows CE." Linux is an attractive option for these devices. ARM can run Windows CE and Linux just fine, so Intel has no real advantage.

Only Atom offers a "real" Internet experience with Flash video, YouTube, etc. Wrong. You can buy ARM Flash players from vendors like BSquare. On2 just announced a YouTube video decoder for ARM. "The Internet doesn't care about the architecture or the operating system," said Jim McGregor, principle analyst at In-Stat. "It creates a level playing field."

Intel dominates every market it enters. This is silly. Intel already tried to dominate the mobile market with its PXA line, and that effort failed. It ended up selling the processor line to Marvell.

Atom will win because ARM is proprietary technology. More nonsense. You can get ARM chips from Freescale, TI, Qualcomm and others.

Intel will win on cost. Intel hasn't announced pricing, but it is obvious that Atom will cost far more than ARM-based chips. An ARM Cortex-A8 occupies less than 3mm x 3mm using a 65nm process. Atom weighs in at 25mm x 25mm using a 45nm process. To be fair to Atom, most of its area is occupied by cache. My analysis suggests that the Atom core itself is about 9mm x 9mm, or three times bigger the size of Cortex-A8. With such a huge area disadvantage, it's hard to see how Intel will win on cost.

Intel will win on power. "Intel admits that the current solution is not as power efficient as the potential ARM competition," said analyst Strauss. Intel quotes thermal design power of 0.6W to 2W for Atom, but doesn't specify the corresponding clock speeds. Comparing this to ARM is a bit tricky, since ARM uses typical power numbers. (TDP is a maximum.) Let's generously assume that Atom's typical power is 50 percent of TDP, as is the case with the AMD Geode LX. This gives us about 300mW at 500MHz. ARM quotes 0.59mW/MHz for the Cortex-A8, which also corresponds to 300mW at 500MHz. Thus, the best-case scenario is that Intel matches ARM. In most scenarios, Atom burns more power.

Intel will win because it has the most advanced fabs. There is a kernel of truth here. Atom will be fabbed in an industry-leading 45nm process using high-k metal gate technology. However, nobody buys chips based on a fab process; consumers focus on cost, power and speed. ARM wins on cost and power. We'll get to speed below.

What they got right
Atom will win on speed. Atom will scale to 1.8GHz speeds, far faster than current ARM offerings. Plus, Atom supports dual-threading (i.e., HyperThreading), which ARM does not.

Atom will be great for PCs. "For low-end PCs, low-end laptops and ultramobile PCs, you don't need gigahertz of performance," said Linley Gwenapp, president and principal analyst at The Linley Group. Atom "should be very good for these PCs." Gwenapp noted that Atom is "a big step in terms of reducing power and cost."

The most important versions of Atom are still a year or two away. The first chip is just a bare CPU. Things will get more interesting with future versions that integrate graphics and a memory controller.

What they missed
Atom will be great for STBs, automotive applications and other connected applications. It might not make sense to run Vista on a mobile device, but the ability to run PC apps would be a godsend for other devices like TiVo and Slingbox. "Having consistent software models as well as the associated standards" is huge, said In-Stat's McGregor. "Being able to seamlessly transfer information among any of these devices enables significant usage models."

Atom can run PC games; ARM can't. This might be the real killer app for Intel. If Intel can leverage the large base of existing PC games it could outflank ARM with mobile gaming devices.

Atom is the basis of many future offerings. Intel has "developed a very low-power core that is going to feed a huge segment of their product line going forward," said McGregor, noting that the Atom architecture will be used in Intel's server accelerators.

Make no mistake: Atom is an important new architecture, and it is likely to be a big success in many markets. Just don't expect it to dethrone ARM in the mobile market segment any time soon.

- Kenton Williston
EE Times

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