I'm currently running a 9.2 kernel (via Nas4Free) on a D525-based system. With the CPU at 0% load and throttled down to 225Mhz, the CPU fan is running at full speed exhausting warm air from the system, which kind of defeats the point of using an Atom-based system (it's supposed to be passively cooled most of the time and near-silent, not with a whiny fan running full tilt 24/7). According to this bug report it's because Atoms don't support C-states, confirmed by a quick check:
(the C2 entry was me playing with rc.conf). This kind of sucks because it means I'm getting less low-power (and most of all silent) usage from a low-power Atom than from a generic desktop CPU. Does anyone know of any way to get some sort of thermal management done under FreeBSD on an Atom-based system? All I've found from web searching is other people with the same problem. The system I'm using it in definitely supports advanced power-management states, it even has front-panel LEDs to indicate the power state that it's in, but it seems like FreeBSD can't take advantage of any of them.
Code:
$ sysctl dev.cpu |grep cx
dev.cpu.0.cx_supported: C1/1/0
dev.cpu.0.cx_lowest: C2
dev.cpu.0.cx_usage: 100.00% last 948us