Tom's Talks Moorestown With The Father Of Centrino

Ticky On Power

TH: Easier said than done, I’m guessing. But to make that happen, you had to conquer power first, right?

TT: Yes, starting with standby power. We had a great, ultramobile, PC-class device platform before. It was low power...but not low enough. So the big challenge for us was to figure out how to deliver low idle power in this kind of form factor. We have work going on in our labs with OSPM—OS Power Management. We want to use Intel’s process strength to get as much out of the process as possible in terms of performance integration and the low active power you can get from the smaller transistors. We introduced the notion of power gating at the island level. We want to use only the power needed to do the activity that you’re doing, not switch on anything else. Today, most operating systems, such as the larger Windows-style OS, do quite the opposite. It’s like opening your front door and the whole house lights up. That’s not what we wanted to do here.

TH: Which explains probably part of why Moorestown for phones doesn’t support PCI and thus Windows, but larger form factor Atom platform versions, including the forthcoming Oaktrail platform, do.

TT: There are many factors at work here. But regardless, we introduced this lowest power management capability that basically allows selective switching off of logical units. When I’m not using, say, the video recording capabilities, the encoder is off. When I’m using only the audio engine, I don’t need the rest of the system on. I only need a little bit of memory and the NAND on. So with active power, we only switch on the circuits needed to do the work. That’s how we achieved our 50x reduction in idle power and over 2x to 3x reduction in active power, while not dropping even a percent in performance .

TH: That seems almost counter-intuitive. In the PC and server worlds, there’s usually some trade-off.

TT: There’s no impact whatsoever in managing performance because when we needed the performance, we enabled it. The key thing there is to get the work done faster and shut down the processor in the platform. That part is very important, because getting that platform in a quiescent state early allows us to actually save more energy by completing the work earlier than if we’d used a slower processor. We deliver higher performance than any of our competitors and save energy during that time.