>I thought the accompanying chipset pushed the baby Atoms up to ~12w total.
This is one of Intel's own motherboards; let me dig it up...D945GCLF.
And I was wrong. The Atom itself has a TDP of 4W. The motherboard claims its total draw is 75W, with hard drive, optical, "and all board peripherals enabled". In practice, I kept it down a lot by installing (a) a laptop hard drive and (b) nothing else. I have a USB optical drive I hook up when I need it.
I should plug it into my Kill-A-Watt tonight and report back--I know I measured it before, but I didn't write down the numbers. I know the idle draw was stupidly low, like under a watt. (That's cheating a little, though, since it means unplugging the dongle for the wireless mouse&keyboard. Even when it's plugged in, it's on a USB hub, which I wasn't measuring.)
Anyway, the Tegra 2 is <2w for complete SoC including the both cores, nvidia gfx, ram and 1Gb storage.
e.g. http://www.netbooknews.com/4891/nvidia-tegra-2-module-fits-o...
TBH, T2 is from 2009, we know Tegra 3 is done and they are already working on Tegra 4 from an interview with the CEO last year