Chapter 4 System Support
Compaq iPAQ Family of Internet Devices
First Edition - March 2000
4-18
Table 4-10 lists the mapping of the configuration memory.
Table 4-10. Configuration Memory (CMOS) Map
Table 4-10.
Configuration Memory (CMOS) Map
Location Function Location Function
00-0Dh Real-time clock 24h System board ID
0Eh Diagnostic status 25h System arc hitecture data
0Fh System res et code 26h Auxiliary peripheral configuration
10h Dis kette drive type 27h Speed c ontrol external drive
11h Res erved 28h Expanded/base mem. siz e, IRQ12
12h Hard driv e type 29h Mis cellaneous configuration
13h Secur ity functions 2Ah Hard drive timeout
14h Equipment ins talled 2Bh System inactivity timeout
15h Base memory size, low by te/KB 2Ch Monitor timeout, Num Lock Cntrl
16h Base memor y size, high byte/KB 2Dh Additional flags
17h Ext ended memory, low byte/KB 2Eh-2Fh Checksum of locations 10h-2Dh
18h Ext ended memory, high byte/KB 30h-31h Total extended memory tested
19h Hard driv e 1, primary controller 32h Century
1Ah Hard drive 2, primary contr oller 33h Miscellaneous flags set by BIOS
1Bh Hard drive 1, secondary controller 34h International language
1Ch Hard drive 2, secondary controller 35h APM status flags
1Dh Enhanced hard drive support 36h ECC POST test single bit
1Eh Reserved 37h-3Fh Power-on passwor d
1Fh Power management functions 40-FFh Feature Control/Status
NOTES:
Assume unmarked gaps are reserved.
Higher locations (>3Fh) contain information that should be acces sed using the INT15, AX=E845h
BIOS function (refer to Chapter 8 for BIOS funct ion descriptions).
4.7.1 CMOS ARCHIVE
There is no pr ovision for clearing the contents of the con figuration memor y (CMOS). During
POST, a copy of the CMOS data is written to a sector of the 82802 FWH. This means that
changes to CMOS will be stored on the following boot. Should th e system hang d uring boot as
the resul t of corrupted CMOS data, th en a Power Butt on Override boot should be invok ed with
the following pr ocedure:
1. Initiate a power cycle by pressing and releasing the Power button, then pressing and holding
the power button for about four seconds so that the system should record a power button
override event.
2. Power down the system.
3. Press and release the power button, initiating a boot sequence. T he system shoul d detect the
occurrence of a power button override event and will load the CMOS archive data stored in
the FWH all owing a successful boot. All passwor ds and settings used in the previous
successful boot wou ld be restored.
4.7.2 STANDARD CMOS LOCATIONS
The following paragraphs describe standard configuration memory locations 0Ah-3Fh. These
locations are a ccessible through usi ng OUT/IN assembly lang uage instruction s using port 70/7 1h
or BIOS function INT15, AX=E823h.