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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.