Compaq MSB900L user manual CMOS RAM Map, BIOS CMOS Setup, Standard BIOS ROM, Digital-Logic Ag

DIGITAL-LOGIC AG MSB900/L Detailed Technical Manual V1.0

5.6.4.1.Standard BIOS ROM

Device:	FWH
Map:	E0000 - FFFFFh	Core BIOS 128k
	C0000 - C7FFFh	VGA BIOS 32k
	CC000 - CFFFFh	FREE

5.6.5.BIOS CMOS Setup

If wrong setups are memorized in the CMOS-RAM, the default values will be loaded after resetting the RTC/CMOS-RAM by de-soldering the battery.

If the battery is down, it is always possible to start the system with the default values from the BIOS.

5.7.CMOS RAM Map

Systems based on the industry-standard specification include a battery backed Real Time Clock chip. This clock contains at least 64Bytes of non-volatile RAM. The system BIOS uses this area to store information including system configuration and initialization parameters, system diagnostics, and the time and date. This information remains intact even when the system is powered down.

The BIOS supports 128Bytes of CMOS RAM. This information is accessible through I/O ports 70h and 71h. CMOS RAM can be divided into several segments:

￿Locations 00h - 0Fh contain the real time clock (RTC) and status information

￿Locations 10h - 2Fh contain system configuration data

￿Locations 30h - 3Fh contain system BIOS-specific configuration data as well as chipset-specific in- formation

￿Locations 40h - 7Fh contain chipset-specific information as well as power management configuration parameters

The following table provides a summary of how these areas may be further divided.

Beginning	Ending	Checksum	Description
00h	0Fh	No	RTC and Checksum
10h	2Dh	Yes	System Configuration
2Eh	2Fh	No	Checksum Value of 10h - 2Dh
30h	33h	No	Standard CMOS
34h	3Fh	No	Standard CMOS - SystemSoft Reserved
40h	5Bh	Yes	Extended CMOS - Chipset Specific
5Ch	5Dh	No	Checksum Value of 40h - 5Bh
5Eh	6Eh	No	Extended CMOS - Chipset Specific
6Fh	7Dh	Yes	Extended CMOS - Power Management
7Eh	7Fh	No	Checksum Value of 6Fh - 7Dh

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