NAME
odcm —
On-demand Clock
Modulation
SYNOPSIS
odcm0 at cpu0
DESCRIPTION
The
odcm driver provides support for changing the duty cycle
of a CPU. This is sometimes known as “on-demand clock modulation”
(ODCM). Refer to
acpicpu(4)
for additional details about ODCM.
The following
sysctl(8)
variables are available with
odcm:
-
-
- machdep.clockmod.target
- The target duty cycle of all CPUs. The values range from 7
(100 %) to 0 (approximately 13 %).
-
-
- machdep.clockmod.current
- The current duty cycle of CPUs.
-
-
- machdep.clockmod.available
- A list of available duty cycles.
Note that some errata may limit the availability of some duty cycles.
SEE ALSO
acpicpu(4),
x86/est(4),
x86/powernow(4)
CAVEATS
ODCM is meant for short-term thermal management, not power management. There is
usually no reason for a system administrator to change the values manually.
Lowering the duty cycle may dramatically decrease performance and
responsiveness of the system.