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4.9 BIOS Data Area Definitions
The BIOS Data Area is an area within system RAM that contains information about the system envi-
ronment. System environment information includes definitions associated with hard disks, diskette
drives, keyboard, video, as well as other BIOS functions. This area is created when the system is first
powered on. It occupies a 256-byte area from 0400h - 04FFh. The following table lists the contents of
the BIOS data area locations in offset order starting from segment address 40:00h.
Location
Description
00h - 07h
I/O addresses for up to 4 serial ports
08h - 0Dh
I/O addresses for up to 3 parallel ports
0Eh - 0Fh
Segment address of extended data address
10h - 11h
Equipment list
bits 15-14 =
bits 13-12 =
bits 11-9= Number of serial adapters
bit 8
bits 7-6 = Number of diskette drives
bits 5-4 = Initial video mode
bit 3
bit 2
bit 1
bit 0
12h
Reserved for port testing by manufacturer
bits 7-1 = Reserved
bit 0
13h
Memory size in kilobytes - low byte
14h
Memory size in kilobytes - high byte
Number of parallel printer adapters
00
=
01
=
10
=
11
=
Reserved
00
=
001
=
010
=
011
=
100
=
= Reserved
00
=
One drive
01
=
Two drives
00
=
EGA or PGA
01
=
40 x 25 color
10
=
80 x 25 color
11
=
80 x 25 monochrome
= Reserved
= (1) Pointing device present
= (1) Math coprocessor present
= (1) Diskette drive present
= (0) Non-test mode
(1) Test mode
57
Not installed
One
Two
Three
Not installed
One
Two
Three
Four
Continued...
PCCP5 Manual V2.3
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