Technical Reference Guide
Compaq Deskpro 4000 and 6000 Personal Computers
featuring the Pentium II Processor
First Edition–- October 1997
4-51
4.8.8 POWER MANAGEMENT
This system includes hardware support of Advanced Power Management (APM) firmware and
software.
4.8.8.1 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.
4.8.8.2 MONITOR POWER CONTROL
The VESA display power management signaling protocol defines different power consumption
conditions and uses the HSYNC and VSYNC signals of the monitor interface to select a
monitor’s power condition. This capability is dependent on the graphics controller employed in
the system. For compliance to the monitor power control feature refer to the applicable appendix
for the installed graphics controller card.
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