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For more details, see Chapter 5.1.2 of the Intel Pentium M
Processor Datasheet.
23.3 Processor Performance Control
The Pentium M processor can run in different performance states
(multiple
frequency/voltage
operating
performance can be altered while the computer is functioning.
This allows the processor to run at different core frequencies
and voltages depending on CPU thermal state and OS policy.
Microsoft
Windows
XP
includes
control to operate the processor more efficiently when it is not
fully utilized. Win2k, WinME and Win9x do not support processor
performance control. Special software is required for Operating
Systems that are not capable of processor performance control.
In Windows, the processor performance control policy is linked
to the Power Scheme setting in the control panel power option
applet.
Notes:
Windows always runs at the highest performance state when the "Home/Office" or the
"Always On" power scheme is selected.
For more detailed information about processor performance control, see:
- Chapter 8 of the ACPI Specification Revision 2.0c
-
Windows platform design notes
23.4 Thermal Management
ACPI allows the OS to play a role in the thermal management of
the system. With the OS in control of the operating environment,
cooling decisions can be made based on the application load on
the CPU and the thermal heuristics of the system.
The
ACPI
thermal
solution
on
cooling policies and their trip points:
†
Active Trip Point
Active cooling devices typically consume power and produce
noise but are able to cool a thermal zone without limiting
system performance. The active cooling trip point declares
the temperature threshold OS uses to start/stop active
cooling devices (fan).
†
Passive Cooling Trip Point
coolMONSTER/PM User's Guide
59
points).
The
CPU
built-in
processor
performance
coolMONSTER/PM
supports
three
Important Technology Information
Passive cooling devices produce no noise, but may not be
effective enough to cool the thermal zone. The passive
cooling trip point declares the temperature threshold in
which the OS will start or stop passive cooling. In this
case it throttles the processor.
†
Critical Trip Point
The OS performs an orderly, but critical, shutdown of the
system when the temperature reaches the critical trip
point.
Processor Clock Throttling
23.4.1
The
ACPI
OS
assesses
the
optimum
necessary to lower the temperature using the following equation:
∆P[%] = TC1(Tn-Tn-1) + TC2(Tn-Tt)
∆P is the performance delta, Tt is the target temperature =
critical trip point. The two coefficients TC1 and TC2 and the
sampling period TSP are hardware dependent constants that you
must supply. (See the setup options in the ACPI Control Submenu
section in the BIOS Operation chapter).
It is up to you to set the cooling preference of the system by
setting the appropriate trip points in the BIOS setup.
Notes: For more detailed information see Chapter 12 of the ACPI Specification.
Important Technology Information
60
KONTRON
CPU
performance
change
coolMONSTER/PM User's Guide
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