Technical Reference Guide
Compaq Deskpro EP Series of Personal Computers
First Edition–- April 1998
4-51
4.8.3 I/O SECURITY
The 87309 I/O controller allows various I/O functions (serial, parallel, diskette I/O) to be
disabled through configuration registers.
4.8.4 POWER MANAGEMENT
This system provides baseline hardware support of ACPI- and APM-compliant firmware and
software. The major power-consuming components (processor, chipset, I/O controller, and fan)
can be placed into a reduced power mode upon software command either automatically or by user
control. The system can then be brought back up (“wake-up”) by any of a number of events
defined by the ACPI specification. The ACPI wake-up events supported by this system are listed
as follows:
ACPI Wake-UpEvent System Wakes From
Power Button Sleep/Soft-Off
RTC Alarm Sleep/Soft-Off
Wake On LAN (w/NIC) Sleep/Soft-Off
PME Sleep/Soft-Off
Serial Ring Sleep/Soft-Off
Voice (w/audio supporting PME) Sleep/Soft-Off
USB Sleep
4.8.4.1 Power Button
This system uses an ACPI-compliant power button that also provides a legacy mode as well. In
legacy mode the system is alternately powered on or off each time button is pressed and released.
In ACPI mode the power supply, when on, will turn off only after the button is pressed and held
for over four seconds. The power button mode is determine by GPO #8, which is controlled by
BIOS during POST. The system also provides several choices regarding the power-up state
following loss of power and these choices are described in Chapter 7 “Power and Signal
Distribution.”
4.8.4.2 Fan Control
All models contain a power supply with a fan that can be turned off by system board logic during
sleep states. The 66-MHz slot 1 system also includes a chassis fan that can be shut off by the
same system board logic. In addition, the chassis fan contains a thermistor that controls fan speed
during normal operation according to the temperature of the air being moved.
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