While exploring new features in NetBSD 4.0_BETA2 I found out that the Enhanced SpeedStep support now works with my server’s Pentium M 760 CPU. The kernel is able to clock the CPU from 2GHz down to 800MHz.
After a few succesful manual experiments I installed the estd package. It provides the Enhanced SpeedStep & PowerNow daemon which monitors the system load and adjusts the CPU frequency accordingly. Because I was curious about the effect I wrote a little shell script which recorded the current CPU frequency every minute. The collected data revealed that the CPU was running at only 800MHz for more than 99% of the time in the last 24 hours.
I’m not sure how much power Enhanced SpeedStep is going to save. But as every little helps I’m enjoying the new slowness of my server.