Cmos Archive And Restore; Standard Cmos Locations - HP Compaq D315 Technical Reference Manual

4.6.2 CMOS ARCHIVE AND RESTORE

During the boot process the BIOS saves a copy of CMOS to the flash ROM. If the system
becomes unusable, the last good copy of CMOS can be recalled using the power-override function
as follows:
1. With the unit powered down, press and release the power button to initiate the boot sequence.
2. Immediately after releasing the power button, press it again and hold (typically at least four
seconds) until the unit powers off again. This action will be recorded as a power button
override event.
3. Press and release the power button once more, initiating the boot sequence that should detect
the occurrence of an override event and load the backup copy of CMOS, allowing the system
to boot.

4.6.3 STANDARD CMOS LOCATIONS

Table 4-11 and the following paragraphs describe standard configuration memory locations 0Ah-
3Fh. These locations are accessible through using OUT/IN assembly language instructions using
port 70/71h or BIOS function INT15, AX=E823h.
Table 4-11. Configuration Memory (CMOS) Map
Location Function
00-0Dh Real-time clock
0Eh Diagnostic status
0Fh System reset code
10h Diskette drive type
11h Reserved
12h Hard drive type
13h Security functions
14h Equipment installed
15h Base memory size, low byte/KB
16h Base memory size, high byte/KB
17h Extended memory, low byte/KB
18h Extended memory, high byte/KB
19h Hard drive 1, primary controller
1Ah Hard drive 2, primary controller
1Bh Hard drive 1, secondary controller
1Ch Hard drive 2, secondary controller
1Dh Enhanced hard drive support
1Eh Reserved
1Fh Power management functions
NOTES:
Assume unmarked gaps are reserved.
Higher locations (>3Fh) contain information that should be accessed using the INT15, AX=E845h
BIOS function (refer to Chapter 8 for BIOS function descriptions).
Table 4-11.
Configuration Memory (CMOS) Map
Location
24h
25h
26h
27h
28h
29h
2Ah
2Bh
2Ch
2Dh
2Eh-2Fh
30h-31h
32h
33h
34h
35h
36h
37h-3Fh
40-FFh
Compaq D315 and hp d325 Personal Computers
Featuring the AMD Athlon XP Processor
Second Edition - April 2003
Technical Reference Guide
Function
System board ID
System architecture data
Auxiliary peripheral configuration
Speed control external drive
Expanded/base mem. size, IRQ12
Miscellaneous configuration
Hard drive timeout
System inactivity timeout
Monitor timeout, Num Lock Cntrl
Additional flags
Checksum of locations 10h-2Dh
Total extended memory tested
Century
Miscellaneous flags set by BIOS
International language
APM status flags
ECC POST test single bit
Power-on password
Feature Control/Status
4-23