Each parameter table has 16 bytes of data. Data from the BIOS ROM is displayed in
hex, least significant byte first. This data breaks down as follows:
Bytes 1 & 2
Number of Cylinders
Byte 3
Number of Heads
Bytes 4 & 5
Not Used
Bytes 6 & 7
Write Precompensation Cylinder
Byte 8
Not Used
Byte 9
Control Byte (= 08H for 8 heads)
Byte 10-12
Not Used
Bytes 13 & 14
Landing Zone 3
Byte 15
Sectors per Track
Byte 16
Not Used
3. There is also a way of using the DOS DEBUG utility to confirm the parameters for
the current drive selected. This is done through the INT 41 (located at d0: 104) and the
INT 46 (located at dO: 118) handlers. INT 41 corresponds to the address of the current
selected parameters for drive 0, and INT 46 corresponds to the address of the current
selected parameters for drive 1.
To see the current selected parameters for drive 0, the proper command at the DEBUG
prompt (-) is:
d0: 104
The first four bytes displayed correspond to the offset (two bytes) and segment 6 (two
bytes) of the location of the selected parameters.
For example, if after entering d0: 104, the result is:
30 IF
00 C8 AB 73.. .<=>Location C800:1F30
[offset] [segment]
then the current selected parameters are located at address C800:1F30. Type
DC800:1F30 at the DEBUG prompt to display the 16 bytes of selected drive parameters.
If, after using the above methods, you verify that the system BIOS does contain the
physical parameter tables for your drives, use WDFMT to low level format the drive,
FDISK (MSDOS 3.3) to partition it, and the "Format C:(D:)/S" command to perform the
high-level format.
