Intel’s Atom

April 14, 2008

Technology editor Bill Wong takes a look at Intel’s new Centrino Atom processor designed for low power, mobile Internet devices (MID) as well as other embedded applications.

William G. Wong

Intel is clearly taking on ARM as well as other low power x86 vendors with its new Centrino Atom product line. Its primary target is mobile Internet devices (MID) but it fits into a wide range of embedded applications as well because it comes in under 3 W. The typical thermal design power range is 0.65 W to 2.4 W with an idle power range of 80 mW to 100 mW.

The Atom is based on Intel’s 45-nm hafnium-based high-k gate transistors. The Z500-series chips, formerly known as Silverthorne, are available in versions from 800 MHz to 1.8 GHz. The 13 mm by 14 mm chip has a 32 Kbyte L1 instruction and 24 Kbyte L1 data cache. There is a 512 Kbyte L2 cache and the chip can handle 1 Gbytes of RAM. The Atom die (Fig. 1) is 25 mm^² that is smaller than the matching 22 mm by 22 mm System Controller Hub (SCH). The SCH combines north and south bridge functionality (Fig. 2). Together the pair is Intel’s smallest platform in this performance range.

The architecture returns to the in-order execution approach with its dual issue, 16-stage pipeline. This is an approach taken by its competitors but a new twist for Intel although it is essentially going back to its roots. The system also employs advances such as combining micro-ops into a single micro-op executed in a single cycle. Dynamic L2 cache sizing helps reduce leakage power in sleep mode.

The system is compatible with Intel's Core 2 Duo instruction set including support for hyper-threading and the new virtualization support. The SSE3 Digital Media Boost instructions are supported but not the newer SSE4 multimedia extensions. It is a reasonable tradeoff given the hardware acceleration in the SCH.

Peripheral Support
The Atom's SCH graphics subsystem implements OpenGL 3D and DirectX 9L support. It has hardware-accelerated 720p and 1080i video decode. On the audio side, the chip includes Intel High Definition Audio support.

The SCH foregoes SATA support for IDE but it does include a pair of 1x PCI Express. It also includes USB host and client support in addition to an SDIO interface. The Atom comes in a 441-pin BGA package. Pricing starts at $45.

This processor is going to be a very interesting platform for both the mobile and deeply embedded space. The 1x PCI Express links match the requirements of applications in this space as well as emerging standards such as the Small Form Factor SIG’s SUMIT specification although it is initially targeted at VIA’s Pico-ITX platform.

Things just got a whole lot more interesting.