Intel’s new Atom processor is a momentous move by the world’s biggest chipmaker. No other x86 processor can match Atom’s combination of low power consumption, small die size, modest manufacturing cost, and good performance. Atom will carry the x86 where it has never gone before—especially into new types of ultramobile systems with wireless Internet connectivity. (Intel calls them “mobile Internet devices,” or MIDs.)
Two things stand out from my analysis of Atom. First, it’s not crippled. It’s an up-to-date 64-bit x86 architecture with the latest virtualization extensions, Supplemental SSE media extensions, and dual Hyper-Threading (some features, such as Hyper-Threading, are optional). Intel decided that 100-percent x86 compatibility is more important than saving power by simplifying the notoriously complex x86 architecture.
Second, Intel slashed power consumption in many little ways without seriously harming performance. Without question, Atom is slower than existing PC processors. But it’s still capable of acceptably running Windows Vista, even with Aero graphics, while drawing significantly less wattage than a typical “low-power” notebook-PC processor. At Intel’s labs in Austin, Texas, I saw production silicon running Vista at a core voltage of just 0.875V while drawing less than one watt. Performance is much better with Linux, which will probably be more common on MIDs.
The design of the front-side bus is but one way the Atom saves power. Normally, Intel processors use Advanced Gunning Transceiver Logic (A/GTL+) to drive this vital I/O interface. Atom uses CMOS logic. It’s slower but draws power only during signal transitions, not while idle. Although the CMOS transceivers save less than half a watt, little things like this add up. And Atom also has A/GTL+ transceivers, so Intel can offer the chip either way.
My only reservation is whether full x86 compatibility is really necessary in MIDs and the other consumer-electronics products that Intel covets for Atom. If full compatibility isn’t vital, Intel has missed a chance to streamline the x86 architecture for greater power efficiency, yielding an advantage to RISC processors. But if the market demands x86 compatibility, Atom has a clear advantage that RISC rivals can’t match.
Tom Halfhill was formerly a senior editor for Byte magazine and is now an analyst for Microprocessor Report.