“In part 1 of this series we learned how to measure how much
power our systems are using, both hardware and software, and some
tricks for reducing power usage without degrading performance.
Today we’re going to dive into the world of power management on
laptops: ACPI, APM, hard disk spindowns, and spinups.
“Power management on laptops is all about squeezing out more
battery time. It’s a losing battle as laptops get more powerful and
use bigger displays. For example, my old Thinkpad R32 runs for
three hours on a charge, even on wireless. My shiny new dual-core
T61 lasts a bit under two hours. The new machine is brighter and
faster, and it has a magnesium roll cage. (Oo la la, like a race
car.) Modern laptops with wide glossy screens are lucky to get