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Via's Nano L2100 takes on Intel's Atom 230

Two new CPU architectures clash on the desktop
— 5:17 PM on July 30, 2008

It would seem that the age of "good enough" computing is upon us. In many cases, what folks want most out of a computer isn't bone-jarring speed or fluid, stunning visuals; it's low power consumption (with the correspondingly long battery life and quiet operation), low cost, stylish design, and performance that, well, doesn't get in the way. The system needs to be adequate to the tasks at hand—typically things like web surfing, email, office productivity applications, and perhaps lightweight media playback. Beyond that, eh, why pay more?

The success of products like the iconic Eee PC and the coming wave of sub-$400 desktop computers have heralded this trend toward good-enough computing. Part of what's driving that trend, of course, is consumer demand, both in traditional PC markets and in the developing world. But the efforts of a couple of PC chipmakers have also played a role in making this trend possible, as design teams for both Intel and Via subsidiary Centaur have been cooking up new PC-compatible CPU architectures aimed at low-power, low-cost systems. Intel, of course, made quite a splash with its introduction of the Atom processor, a teeny sliver of a chip intended to extend PC compatibility into much smaller devices, including GPS receivers and eventually smart phones. Meanwhile, Via introduced a sophisticated new CPU, dubbed Nano, that promises more than double the performance of its C7 processors inside of power envelopes as small as 5W.

Comparisons between the Atom and Nano were pretty much inevitable. Beyond the Lilliputianistic names and the shared emphasis on keeping costs and power use low, the chips were both designed in Austin, Texas and first introduced to the public just weeks apart. Yet if you ask Intel or Via about it, they'll both tell you that the CPUs aren't really natural rivals on all fronts. The Atom is a smaller, simpler chip that can go places the Nano can't, thanks to much lower power envelopes for many Atom models. Meanwhile, the Nano looks to break new performance ground for what is essentially a commodity x86 processor.

One place where these two rivals will undoubtedly meet is in low-cost desktop systems, like Asus' Eee Box. Here, Nano and Atom will square off in their fastest configurations, those least concerned about power use and most oriented toward performance. And, happily, this is the ground on which we have our first glimpse of both CPU architectures, in the form of the Atom 230 and Nano L2100 processors. These poor little chips have been gallantly laboring away under the weight of our semi-appropriate benchmark suite in Damage Labs for the past little while. Keep reading to see how they match up.

The Nano L2100
If you're not familiar with the basics of the Nano's microarchitecture, let me suggest you go read our article on the subject. One of the biggest things that distinguishes it from the Atom is the Nano's use of both out-of-order and speculative execution, techniques commonly employed to extract more instruction-level parallelism out of code being executed. Via's older processors, including the C7 and its forbears, kept to in-order execution, as does the Atom. As a result, the Nano promises higher clock-for-clock performance than any of them.

The Nano's clock speeds aren't bad, either, at least in desktop form. The L2100 chip we're testing today is clocked at 1.8GHz, with an 800MHz front-side bus. With a 64KB L1 instruction cache, a 64KB L1 data cache, and a 1MB L2 data cache, the L2100 sounds every bit like a modern CPU. That impression is deepened by its support for many of the latest extensions to the x86 instruction set architecture, including SSE/2/3, Supplemental SSE3, and the x86-64 extensions for 64-bit computing.

Via estimates the Nano's transistor count at 94 million. The chips are manufactured by Fujitsu on a 65nm fabrication process, and they come out to be 63.3 mm² in total die area. Nano models range in clock speed from 1GHz to 1.8GHz and in TDP (thermal design power, their maximum power and thermal envelopes) from 5W to 25W. The L2100 is at the top end of the spectrum, with a TDP of 25W. Still, Via claims an idle power draw of only 500 mW for the L2100, not much greater than the 100 mW rated idle draw of the rest of the Nano line, even though most L2100-based systems will likely spend their days plugged into a wall socket.

Nano processors aren't available for purchase just yet, but one of their virtues when they arrive will be pin-compatibility with the C7, which should make for easy product upgrades for Via and its partners. Via illustrated this fact by supplying us with a pre-production Nano test setup that's nothing more than a Nano L2100 soldered onto an EPIA SN motherboard, a product that's currently selling with a C7 onboard.

The EPIA SN is a Mini-ITX-sized board that crams in a surprising amount of functionality, including dual DDR2 DIMM sockets, four SATA ports, one ATA port, a pair of Ethernet ports (one Fast, one Gig), multichannel audio outputs, a VGA port, and even a PCI Express x16 slot for graphics cards. You can't see them in the picture above, but on the underside of the board are two more connectors: a Compact Flash slot and a mini-PCI expansion slot. Via likes to point out that such robust expansion options are possible on a Nano motherboard because it enforces no restrictions on component makers with regard to such things. By contrast, Intel has reportedly set limits on how Atom processors may be used in products; among those limitations is the prohibition both of PCI Express slots and of the inclusion of more than one DIMM slot.

The EPIA SN is powered by the core-logic combination of the CN896 north bridge and the now-venerable VT8251 south bridge chip. The CN896 includes an embedded Chrome9 HC graphics processor, based on GPU technology from Via subsidiary S3 Graphics. At present, Via is the only supplier of Nano chipsets, although rumors about a possible Nvidia chipset have been swirling for a while now.

Unfortunately, despite its relative maturity, we ran into several problems with the Via chipset on the EPIA SN. The SATA controller's AHCI function isn't really supported properly; Via's latest Hyperion driver package lacks a Windows XP driver for AHCI, and installing the Hyperion drivers on Vista x86 with AHCI enabled caused our system not to boot. The SATA ports work well enough in IDE mode, but you'll have to do without support for SATA device hot-swapping and Native Command Queuing. (We've seen similar problems with most of AMD's recent chipsets, which isn't an excuse, just an observation.) Even more annoyingly, the EPIA SN's VGA port produces soft, smeary output that makes text difficult to read. Since the board lacks a digital video output like DVI, this is an especially unfortunate problem. This signal quality issue might be more of a motherboard-level problem than a chipset one, so we're hopeful that it may not affect all CN896-based systems.

Since this is pre-release hardware, of course, some minor snags are probably inevitable. We were still somewhat disappointed to see that the EPIA SN board and BIOS didn't appear to support the Nano's dynamic clock speed and voltage scaling capabilities, a la Intel's SpeedStep. Via assures us that all versions of the Nano, including the L2100, do include this capability, and I'd hope to see this problem ironed out on production hardware.

We ran into another problem while working with the Nano that doesn't look to be the fault of the chipset or of Via's hardware at all. As detailed in this Microsoft Knowledgebase article, the 64-bit versions of Windows Vista (and, we found, Windows XP Pro x64) won't install on a Nano-based computer. The problem, it seems, is that the Windows installer is looking for a CPUID string that says either "GenuineIntel" or "AuthenticAMD". When it runs into "CentaurHauls", it keels over and dies in a splash of blue across the screen. Microsoft does have a hotfix available for Vista x64, but it's tough to install a hotfix prior to installation of the OS. You've got to slipstream the hotfix into a custom Vista install image. Given limited time for the preparation of this article, we chose to test with Vista x86 instead.

Via says we can expect the first Nano-based products to hit the market "towards the end of this quarter." Among the first wave of products will be netbook systems similar to the Eee PC (likely based on Via's OpenBook reference design), larger laptops in the "thin and light" category, and small form factor desktops.