Equipment Byte - IBM Personal System/2 50 Technical Reference

Equipment Byte (Hex 014): The equipment byte defines the basic
equipment in the system for the power-on diagnostic tests.
Bit Function
7.6 Number of Diskette Drives
5. 4 Display Operating Mode
3. 2 Reserved
1 Math Coprocessor Presence
o
Diskette Drive Presence
Figure 3-20. Equipment Byte
Bits 7, 6 These bits indicate the number of diskette drives installed,
as shown in the following figure.
Bits Number of
76
Diskette Drives
00 One Drive
01 Two Drives
10 Reserved
1 1 Reserved
Figure 3-21. Equipment Byte (Bits 7, 6)
Bits 5, 4 These bits indicate the operating mode of the display
attached to the video port, as shown in the following
figure.
Bits Display
54
Operating Mode
00
Reserved
01 4D-Column Mode
10 aD-Column Mode
1 1 Monochrome Mode
Figure 3-22. Equipment Byte (Bits 5, 4)
Bits 3, 2 Reserved.
Bit 1 When set to 1, this bit indicates that a math coprocessor is
installed.
Bit 0 When set to 1, this bit indicates that a diskette drive is
installed.
3-22 Model 50 System Board