The Atom 230
We've already covered the Atom's microarchitecture in some detail, so I suggest reading that article if you want to know more about it. The highlights include a simple design with in-order execution. The Atom design team specifically vetted potential performance-enhancing features for efficiency, leaving out some familiar enhancements along the way. One feature that did make the cut and would seem to fit nicely with the Atom's in-order pipeline is simultaneous multithreading, better known by the Intel marketing name Hyper-Threading. A single Atom core supports two hardware threads, achieving some additional performance via parallelism at the thread level rather than the instruction level.
Like the Nano, the Atom 230 we're reviewing supports a robust portion of the alphabet soup of extensions to the x86 ISA, including SSE/2/3/SSSE3 and EM64T, Intel's version of x86-64. It doesn't support SSE4, nor does the Nano. There has been confusion in some quarters, because some lower-power versions of the Atom lack 64-bit support, but the architecture is fully 64-bit capable. Our Atom 230 had no trouble with installing and running Windows Vista x64 Edition (although we used the x86 version for our comparative testing against the Nano). In fact, one of the reasons Intel chose to create a new chip rather than dusting off an older design was to ensure compatibility with the latest CPU features and extensions.
The 230 is currently the lone desktop variant of the Atom, clocked at 1.6GHz on a 533MHz front-side bus. The chip includes a 32KB L1 instruction cache, 24KB L1 data cache, and a 512KB L2 cache. Intel manufactures this processor on its high-k 45nm fab process, and the Atom's roughly 47 million transistors are jammed into a die that's only 24.2 mm²under half the size of the 65nm Nano. Despite having a similar clock speed, the Atom 230 has a TDP rating of just 4W, vastly less than the Via chip. Other Atom models range from 2.5W TDP all the way down to 0.65W, well below the Nano's lowest power envelope.
Intel enforces the Atom 230's desktop focus by disabling a key feature needed for mobile chips: SpeedStep, the combination dynamic of voltage and clock speed scaling capabilities that's de rigueur even in most desktop-class processors these days. The loss of this feature isn't likely to matter greatly to any desktop PC; the Atom 230 is still going to run very cool and quiet at idle compared to most CPUs. One benefit of the product segmentation is Intel's willingness to sell the Atom 230 really stinkin' cheap: they're priced at only $29, whereas the 1.6GHz mobile variant costs $44. (Via hasn't disclosed exact Nano pricing to us.)
Such incredibly low CPU prices enable board makers to offer creations like this one: the Intel D945GLCF. This mobo comes complete with a soldered-on Atom 230 processor for about 69 bucks.
No, really. 69 bucks. With built-in audio, 10/100 Ethernet, and video. And the video output is much crisper than on the VIA EPIA board. We are talking about a low-cost desktop here, folks. I've gotta admit, just seeing this combination of size and features for this price makes me feel old. I paid how much for my Amiga 3000? Don't remind me.
As the name hints, this mobo is based on Intel's 945 chipset, with a 945GC MCH and an ICH7 south bridge. These are the components of the Atom's "Diamondville" platform, which will be used in both low-cost desktops and in netbooks like the Eee PC 901. (The versions of the Atom intended for smaller, lower-power devices will use the "Poulsbo" core-logic chip and will be imprinted with the Centrino Atom brand.) Note that, in the picture above, the larger heatsink with the fan onboard is used to cool the 945GC MCH chip, while the little, stubby heatsink next to it covers the Atom processor. This arrangement may tell you everything you need to know about the Atom's current platform situation.
The D945GCLF seems like a compelling bargain, but its limitations are also obvious: the single DIMM slot, the lone PCI expansion slot, and neither an AGP nor a PCIe x16 graphics slot. As you might have guessed from the motherboard's dimensions, Intel has embraced Via's Mini-ITX form factor, and will apparently be limiting Atom desktop boards to this template. If this motherboard's specs do indeed represent the practical ceiling for Atom desktop expandability, that would be a shame. I saw Atom-based systems with discrete graphics cards running recent PC games rather well during a tour of Intel's qualification labs in Austin. Better things are possible, although perhaps Intel would prefer to counter the more expandable Nano-based systems with a different processor, maybe something from the Celeron range.
Side by side
Here's a look at the Atom and Nano boards situated next to each other with their heatsinks removed. The Atom is on the left and the Nano's on the right, with a quarter dropped in between them as a size reference. In both cases, the larger chip visible on the board, not far from the CPU, is the chipset's north bridge and integrated graphics processor. The Atom is clearly a much smaller chip than the Nano, but the packaging for the two processors is almost the exact same size, interestingly enough.