Make CPU Idle calls when idle


Linux Kernel Configuration
└─>Power management and ACPI options
└─>APM (Advanced Power Management) BIOS support
└─>Make CPU Idle calls when idle
In linux kernel since version 2.6.12  
Enable calls to APM CPU Idle/CPU Busy inside the kernel's idle loop.
On some machines, this can activate improved power savings, such as
a slowed CPU clock rate, when the machine is idle. These idle calls
are made after the idle loop has run for some length of time (e.g.,
333 mS). On some machines, this will cause a hang at boot time or
whenever the CPU becomes idle. (On machines with more than one CPU,
this option does nothing.)