System Support

4.4.2 Standard CMOS Locations

Table 4-6 describes 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 4-6.

Configuration Memory (CMOS) Map

Location

Function

Location

Function

00-0Dh

Real-time clock

24h

System board ID

0Eh

Diagnostic status

25h

System architecture data

0Fh

System reset code

26h

Auxiliary peripheral configuration

10h

Diskette drive type

27h

Speed control external drive

11h

Reserved

28h

Expanded/base mem. size, IRQ12

12h

Hard drive type

29h

Miscellaneous configuration

13h

Security functions

2Ah

Hard drive timeout

14h

Equipment installed

2Bh

System inactivity timeout

15h

Base memory size, low byte/KB

2Ch

Monitor timeout, Num Lock Cntrl

16h

Base memory size, high byte/KB

2Dh

Additional flags

17h

Extended memory, low byte/KB

2Eh-2Fh

Checksum of locations 10h-2Dh

18h

Extended memory, high byte/KB

30h-31h

Total extended memory tested

19h

Hard drive 1, primary controller

32h

Century

1Ah

Hard drive 2, primary controller

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 password

1Fh

Power management functions

40-FFh

Feature Control/Status

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).

4.5 System Management

This section describes functions having to do with security, power management, temperature, and overall status. These functions are handled by hardware and firmware (BIOS) and generally configured through the Setup utility.

4.5.1 Security Functions

These systems include various features that provide different levels of security. Note that this subsection describes only the hardware functionality (including that supported by Setup) and does not describe security features that may be provided by the operating system and application software.

 

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