CPU(4) OpenBSD Programmer's Manual (i386) CPU(4)NAMEcpu - Central Processing Unit
SYNOPSIS
cpu0 at mainbus?
cpu* at mainbus?
DESCRIPTION
Several processor models have additional features that extend their base
functionality, such as power and frequency control or thermal monitoring.
FREQUENCY CONTROL
The sysctl(3) hw.cpuspeed will return the current operating frequency of
the processor (on some processors this value may be an approximation).
If possible, speed may be adjusted by altering hw.setperf from 0 to 100,
representing percentage of maximum speed. There are several possible
implementations for setperf, all transparent to the user. In systems
with more than one control capability, they are preferred in the order
given.
LongRun Found on Transmeta Crusoe processors, offers frequency
scaling with numerous positions. The processor dynamically
adjusts frequency in response to load, the setperf value is
interpreted as the maximum.
EST Enhanced SpeedStep found on Intel Pentium M processors,
offers frequency scaling with numerous positions.
SpeedStep Found on some Intel Pentium 3 and newer mobile chips, it is
capable of adjusting frequency between a low and high value.
Only enabled on some chipsets.
TCC Thermal Control Circuit found on Intel Pentium 4 and newer
processors, adjusts processor duty cycle in 12.5 percent
increments.
PowerNow Found on various AMD processors. Currently only supports a
limited set of models in the K6, K7, and K8 families.
INSTRUCTION SET EXTENSIONS
The presence of extended instruction sets can be determined by sysctl
machdep.
osfxsr Supports the fxsave instruction.
sse Supports the SSE instruction set.
sse2 Supports the SSE2 instruction set.
xcrypt Support the VIA AES encryption instruction set. If this is
supported, the libcrypto EVP AES functions will automatically
use this support.
THERMAL MONITORING
The sysctl(3) hw.sensors.cpu*.temp0 will return the current temperature
reported by the processor.
SEE ALSOsysctl(8)BUGS
Due to the way in which thermal information is reported on Intel
processors, the temperature may be off by exactly +/-15 degrees C.
For multiprocessor kernels with more than one CPU sensor, processors will
report identical temperatures since the temperature is taken from the
processor running the sensors update.
OpenBSD 4.9 July 13, 2009 OpenBSD 4.9