Compaq 850 manual Configuration Byte 24h, System Board Identification

Chapter 4 System Support

Configuration Bytes 19h-1Ch, Hard Drive Types

Byte 19h contains the hard drive type for drive 1 of the primary controller if byte 12h bits <7..4> hold 1111b. Byte 1Ah contains the hard drive type for drive 2 of the primary controller if byte 12h bits <3..0> hold 1111b. Bytes1Bh and 1Ch contain the hard drive types for hard drives 1 and 2 of the secondary controller.

Configuration Byte 1Dh, Enhanced IDE Hard Drive Support

Default Value = F0h

Bit Function

7EIDE - Drive C (83h)

6EIDE - Drive D (82h)

5EIDE - Drive E (81h)

4EIDE - Drive F (80h)

3..0 Reserved

Values for bits <7..4> : 0 = Disable

1 = Enable for auto-configure

Configuration Byte 1Fh, Power Management Functions

Default Value = 00h

Bit	Function
7..4	Reserved

3Slow Processor Clock for Low Power Mode 0 = Processor runs at full speed

1 = Processor runs at slow speed

2	Reserved
1	Monitor Off Mode
	0	= Turn monitor power off after 45 minutes in
	standby
	1	= Leave monitor power on

0Energy Saver Mode Indicator (Blinking LED) 0 = Disable

1 = Enable

Configuration Byte 24h, System Board Identification

Default Value = 7Eh

Configuration memory location 24h holds the system board ID.

Configuration Byte 25h, System Architecture Data

Default Value = 0Bh

Bit Function

7..4 Reserved

3Unmapping of ROM: 0 = Allowed

1 = Not allowed

2	Reserved
1,0	Diagnostic Status Byte Address
	00	= Memory locations 80C00000h-80C00004h
	01	= I/O ports 878h-87Ch
	11	= neither place

4-26Compaq Deskpro EXS and Workstation 300 Personal Computers Featuring the Intel Pentium 4 Processor

First Edition - December 2000