IBM AT 5170 Technical Reference page 80

Bit 3-Bit 2
Bit 1
Bit 0
01 Primary display is in the 40-column mode
and attached to the Color/Graphics
Monitor Adapter.
10 Primary display is in the 80-column mode
and attached to the Color/Graphics
Monitor Adapter.
11 Primary display is attached to the
Monochrome Display and Printer Adapter.
Not used.
Math Coprocessor presence bit:
o
Math Coprocessor not installed
1 Math Coprocessor installed
Diskette drive presence bit:
o
Diskette drive not installed
1 Diskette drive installed
Note: The equipment byte defines basic equipment in the
system for power-on diagnostics.
Low and High Base Memory Bytes (Hex 15 and 16)
Bit 7-Bit 0
Address hex I5-Low-byte base size
Bit 7-Bit 0 Address hex I6-High-byte base size
Valid Sizes:
0100H
0200H
0280H
256K-system board RAM
5I2K-system board RAM
640K-5I2K system board RAM
and the IBM Personal Computer
AT 128KB Memory Expansion
Option
1-64 System Board