MS-DOS 3.20: Disk Parameters for 80-Track-Per-Side Drives
ID Number:  Q11276

3.20
MS-DOS


Problem:

Table 3.2 on Page 3-11 of the "Microsoft MS-DOS Programmer's
Reference" shipped with both the Alpha and Beta versions of MS-DOS
Version 3.20 shows some disk parameters for 80-track-per-side drives
that differ from versions of the parameters published in the past.
Have these parameters changed?

Response:

The parameters have not changed. Some of the information in the table
is incorrect. The errors are as follows:

1. The number of root directories for the single-sided 8-sector format
   (the first column of numbers) and the single-sided 9-sector format
   (the second column of numbers) should be 112, not 64 as listed in
   the table.

2. The total number of sectors for the double-sided 9-sector format
   (the fourth column of numbers) should be 1440, not 1640 as shown in
   the table.

3. The Media Descriptor for the single-sided 9-sector format (the
   second column of numbers) should be F8, not FB as shown in the
   table.

4. The Media Descriptor for the double-sided 8-sector format (the
   third column of numbers) should be FB, not F8 as shown in the
   table.

The following is a corrected copy of the table:

Table 3.2 MS-DOS Standard Disk Formats

Disk Size             3.5 or 5.25                  5.25
in inches

Tracks/side        80    80    80    80              80

WORD Bytes/
  Sector          512   512   512   512             512

BYTE Sectors/
  Allocation unit   2     2     2     2               1

WORD Reserved
  Sectors           1     1     1     1               1

BYTE No. FATs       2     2     2     2               2

WORD Root Dir
  Entries         112   112   112   112             224

WORD No. Sectors  640   720  1280  1440            2400

BYTE Media
  Descriptor       FA    F8    FB    F9              F9

WORD Sectors/
  FAT               1     2     2     3               7

WORD Sectors/
  Track             8     9     8     9              15

WORD No. Heads      1     1     2     2               2

WORD No. Hidden
  Sectors           0     0     0     0               0
