Browse Prior Art Database

Technique for Monitoring a Computer System's Activity for the Purpose of Power Management of a DOS-Compatible System

IP.com Disclosure Number: IPCOM000101967D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 4 page(s) / 175K

Publishing Venue

IBM

Related People

Ballou, RV: AUTHOR [+3]

Abstract

This article describes a technique and circuit design which allows a portable personal computer (PC) system that is equipped with power-saving circuitry to be placed in a power-save mode by determining to a high degree of certainty that the system is idle.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 39% of the total text.

Technique for Monitoring a Computer System's Activity for the Purpose of Power Management of a DOS-Compatible System

       This article describes a technique and circuit design
which allows a portable personal computer (PC) system that is
equipped with power-saving circuitry to be placed in a power-save
mode by determining to a high degree of certainty that the system is
idle.

      Conventionally, power-saving techniques for portable computers
has mostly taken the approach of saving the state of the machine
after some given amount of time goes by without a key being pressed
and then removing power from the system.  This works well except in
cases where the machine is executing programs that do not require
keyboard input for an extended period of time.  The risk is run in
this situation of shutting down the system while it is still doing
useful work.  Another drawback is the time required to bring the
system out of its power-save mode.  In many cases this time can
stretch into several seconds.  This amount of time is normally not
significant, but when the system is being used as a terminal via an
RF radio link or through a telephone modem, this latency would be
unacceptable. Disclosed herein is a technique involving a balance of
hardware and software that allows a system to determine whether the
system is currently inactive, and if found to be so, it can take
actions to decrease the amount of power being consumed.  This
approach also allows the system to detect a ring in the case of the
telephone modem.  It monitors any type of input/output (I/O) activity
and can bring the system back to full operation in a few
microseconds.

      In the disclosed technique the PC system is separated into a
series of subsystems that are independently powered by
software-controlled power supplies.  The power to these subsystems is
switched on when the subsystem is needed, and can be switched off
automatically when the system is deemed to be idle by the monitoring
circuit.  Whether a subsystem is turned on/off automatically by the
power management software is defined by the user in a system profile
that the user configures.

      Beyond controlling the subsystem power supplies, this design
allows for the implementation of a SLEEP mode for the subsystem.
This SLEEP mode involves slowing down the processor clock and putting
it in a halt state to conserve power.  The power savings of this
approach are due to the nature of complementary metal oxide
semiconductor (CMOS) logic, which draws the vast majority of the
power while switching from one logic state to the other.
Consequently, decreasing the number of logic transitions per unit
time achieves a proportionate decrease in the power consumed.
Halting the processor eliminates all transitions on the bus.  This
optimizes current drain since the processor support logic and the
memory reduce their power consumption to leakage and standby levels,
respectively, thus decreasing the current...