Compaq 4000N User Manual download pdf (Page 90)

Chapter 4 System Support

Compaq Deskpro 4000N and 4000S Personal Computers

First Edition - September 1997

4-48

4.7.6 POWER MANAGEMENT

This system includes hardware support of Advanced Power Management (APM ver. 1.2)

firmware and software and is Energy Star-compliant.

4.7.6.1 HARD DRIVE SPINDOWN CONTROL

The timeout parameter stored in the SIT record 04h and indexed through CMOS location 2Ah

(bits <4..0>) represents the period of hard drive inactivity required to elapse before the hard drive

is allowed to spin down. The timeout value is downloaded from CMOS to a timer on the hard

drive. The timeout period can be set in incremental values of 0 (timeout disabled), 10, 15

(default), 20, 30, and 60 minutes. A timed-out and spun-down hard drive will automatically spin

back up upon the next drive access. It is normal for the user to detect a certain amount of access

latency in this situation.

4.7.6.2 DISPLAY MONITOR POWER MANAGEMENT CONTROL

This system supports monitor power control for graphics controllers and display monitors that

conform to the VESA display power management signaling (DPMS) protocol. This protocol

defines different power consumption conditions and uses the HSYNC and VSYNC signals to

select a monitor’s power condition This operation is described in chapter 6, “Graphics

Subsystem.”

The timeout parameter set in the SIT record 03h and indexed at CMOS location 2Ch (bits

<4..0>) represents the period of system I/O inactivity required to elapse before the monitor is

placed into Suspend mode.

A separate timer function (enabled through CMOS location 1Fh, bit <1>) can be enabled to place

the monitor into the Off mode after 45 minutes of being in Suspend mode.

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Compaq 4000N User Manual Page 90