The Atom processor was something of a surprise success for Intel. The company expected its product to succeed, of course, but perhaps not in the manner it did. When we first visited the Atom's Austin, Texas-based design team, the spotlight was firmly affixed on the low-power Menlow platform. Intel expected Menlow to find its way into several different sorts of handheld mobile devices, including GPS receivers and portable game players. Most notably of all, it hoped to see a new category of Atom-based products, variously called ultra-mobile PCs (UMPCs) and mobile Internet devices (MIDs), become a consumer favorite. The other, larger Atom platform, code-named Diamondville and aimed at low-cost notebooks and desktops, was almost an afterthought.
Yet even at that time, the prospects for a UMPC revolution seemed dim, particularly in light of the iPhone's rising popularity. What happened instead was the explosion of low-cost netbooks, scads of 'em, as a robust new product category, almost all of them based on Diamondville. Suddenly the Atom was everywhere, just not in the form Intel had anticipated.
The reasons for Menlow's relative unpopularity were no great mystery. Although the Menlow platformcomprised of the Silverthorne processor and the Poulsbo chipsetwas smaller and required less power than any prior PC-compatible solution, it was still too big and power-hungry to fit into traditional smart phones and the like. With MIDs moribund, Menlow was stuck between classes, a product without a true home. Intel's attempts to lure phone makers away from ARM processors predictably gained little traction.
Then again, Menlow was only a first step. Intel's plans for the Atom have long called for reductions in the size and power draw of the Atom platform while keeping computing power relatively steady. Late last year, Diamondville gave way to Pine Trail, with one third of the physical footprint and 40% lower max power consumption, ushering in a wave of netbooks with up to 10 hours of battery life for under $300. Increased integration made that change possible even without a move to a newer chip fabrication process. Now, the second-generation low-power Atom platform, code-named Moorestown, is poised to take a much larger step into wholly new territory for an x86 processor: directly into the size and power requirements of smart phones and tablets.
To get there, the design team has conducted a sweeping revamp of the Atom platform, integrating more components into the main chip and making extensive modifications throughout to reduce power consumption. The result is a claimed 50X reduction in platform-wide idle power draw versus Menlow, in a package that takes up 40% less area, mounted on boards half the size of the previous generation. Intel believes Moorestown is competitive with existing smart phone platforms in terms of size and power efficiency, but with roughly double the performance. The Atom has the added benefit of x86 compatibility, for whatever that's worth in the realm of handheld devices. We recently visted Intel's Austin Design Center to learn more about Moorestown, and it was an education in what's required to shrink a PC-compatible system into a pocket-sized form factor.
The Lincroft SoC
Technically, a trio of chips makes up the Moorestown platform, but don't let that fact fool you. Moorestown is more tightly integrated than ever before and will require fewer auxiliary chips in order to function. The most noteworthy of the three chips is code-named Lincroft, and it has enough platform elements integrated into a single piece of silicon that Intel calls it a system on a chip, or SoC. Inside the Lincroft SoC resides an Atom CPU core, a front-side bus interconnect, a memory controller, a 3D graphics core, video playback and encoding units, and a display engine. The companion Langwell platform controller hub (PCH) chip handles traditional I/O duties, and the Briertown MSIC largely serves as a platform power manager. We'll take a look at each one in turn, starting with Lincroft.
You might be surprised to learn that Lincroft isn't being manufactured using Intel's latest 32-nm fabrication process, even though the firm has been shipping 32-nm desktop and server processors for months. Instead, Lincroft is built using a variant of Intel's 45-nm, high-k metal gate process tailored for low-power applications. One benefit of this process is the ability to use multiple transistor types, something the Atom team says they've done for Lincroft. They declined, however, to reveal any specifics about how the different transistor types are being used.
Generally, we've seen two different transistor types deployed in low-power processor designs: a slower variant with lower leakage for circuitry not in the critical performance path, plus a faster variant with higher leakage for gates that must switch quickly. We expect Intel is doing something along those lines with Lincroft, which would explain how they're able to claim a 60% reduction in leakage power with negligible performance loss.
The custom SoC process also enables integration by supporting the higher voltages required by some types of I/O, including display standards like LVDS.
All told, Lincroft measures 7.3 mm by 8.9 mm, or 65.3 mm², with roughly 140 million transistors packed into that space. That's quite a bit larger than the prior-gen Silverthorne Atom, whose 47 million transistors occupied just over 24 mm², but moving more components from the chipset into Lincroft's 45-nm silicon is almost certainly an advantage. Crucially for its intended market, Lincroft's package is still relatively small at 13.8 mm by 13.8 mm.