Does the Linux kernel execute the Halt instruction to power down the CPU?
• (REG, ADB) Yes. The Linux kernel will execute the Halt instruction when the machine is idle (check the code for the idle_task in sched.c). It has done so since the earliest i386 implementation, even though on the i386 we didn’t care about power saving; it’s just that halting the CPU is the Right Thing ™ to do when there is no other task that must be run. On the Pentium, K6 and C6 CPUs, power consumption gets automatically reduced from an average 12-24 Watts operating power down to 2-3 Watts when the processor is Halted. On the Cyrix 6×86 CPUs, Halt state power consumption can be further reduced down to 150 mw by enabling the Suspend-on-Halt feature. Reduced power consumption means cooler, more reliable machine operation and longer component life. And it saves trees too.
• (REG, ADB) Yes. The Linux kernel will execute the Halt instruction when the machine is idle (check the code for the idle_task in sched.c). It has done so since the earliest i386 implementation, even though on the i386 we didn”t care about power saving; it”s just that halting the CPU is the Right Thing ™ to do when there is no other task that must be run. On the Pentium, K6 and C6 CPUs, power consumption gets automatically reduced from an average 12-24 Watts operating power down to 2-3 Watts when the processor is Halted. On the Cyrix 6×86 CPUs, Halt state power consumption can be further reduced down to 150 mw by enabling the Suspend-on-Halt feature. Reduced power consumption means cooler, more reliable machine operation and longer component life. And it saves trees too.
