Editing Advanced Power Management (section)

== Hardware components ==

=== CPU ===
The CPU core (defined in APM as the CPU clock, [[CPU cache|cache]], [[Front-side bus|system bus]] and system timers) is treated specially in APM, as it is the last device to be powered down, and the first device to be powered back up. The CPU core is always controlled through the APM BIOS (there is no option to control it through a driver). Drivers can use APM function calls to notify the BIOS about CPU usage, but it is up to the BIOS to act on this information; a driver cannot directly tell the CPU to go into a power saving state.

=== ATA drives ===
The [[Parallel ATA|ATA]] specification and [[SATA]] specification defines APM provisions for hard drives, which specifies a trade-off between spin-down frequency and always-on performance. Unlike the BIOS-side APM, the ATA APM and SATA APM has never been deprecated.<ref>{{cite web |title=linux - What do different values of hard drive's Advanced Power Management feature (hdparm -B) affect, except spin-down? |url=https://superuser.com/a/558622 |website=Super User |quote=The ATA Spec turns up this tidbit:  Subcommand code 05h allows the host to enable Advanced Power Management. To enable Advanced Power Management, the host writes the Sector Count register with the desired advanced power management level and then executes a SET FEATURES command with subcommand code 05h.}}</ref>

Aggressive spin-down frequencies may reduce drive lifespan by unnecessarily accumulating load cycles; most modern drives are specified to sustain 300,000 cycles and usually last at least 600,000. On the other hand, not spinning down the drive will cause extra power draw and heat generation; high temperatures also reduce the lifespan of hard drives.<ref>{{cite web |last1=bwDraco |title=linux - How much "Load_cycle_count" can my hard drive hypotethically sustain? |url=https://superuser.com/a/847431/ |website=Super User}}</ref>