IBM AT 5170 Technical Reference page 77

Shutdown Status Byte (Hex OF)
The bits in this byte are defined by the power on diagnostics. For
more information about this byte, see "BIOS Listing. "
Diskette Drive Type Byte (Hex 10)
Bit 7-Bit 4 Type of first diskette drive installed:
0000
0001
0010
No drive is present.
Double Sided Diskette Drive (48 TPI).
High Capacity Diskette Drive (96 TPI).
Note: 0011 through 1111 are reserved.
Bit 3-Bit 0 Type of second diskette drive installed:
0000
0001
0010
No drive is present.
Double Sided Diskette Drive (48 TPI).
High Capacity Diskette Drive (96 TPI).
Note: 0011 through 1111 are reserved.
Hex address 11 contains a reserved byte.
System Board 1-61