Appendix
J
Physical Format
Of
Hard
Disks
CP/M-86
restricts the maximum size
of
a disk
to
8MB. The APC
hard
disk units
have a
10MB capacity. Therefore, to maintain compatibility with
CP/M-86,
the
APC
CBIOS views each physical
hard
disk unit as two logical disk drives. This
structure provides additional benefits.
• The drives may be initialized independently.
• Free space
is
allocated independently for the two drives.
• The system can physically copy from one drive to the other.
The system
supports
up
to two physical
hard
disk units, labelled 0
and
1.
The drives
are labelled E
and
F (unit 0), G
and
H (unit
1).
PHYSICAL FORMAT
Each drive
is
organized in the following format, as shown in Figure J-1.
• 89.5 cylinders
• 562 allocation blocks
• 4.60MB disk space
• 24 tracks free space (for track reallocation)
The disk space
is
organized as follows:
• 256 bytes/sector
•
26
sectors/track
(0-25)
• 8 tracks/cylinder (0-7)
•
181
cylinders/unit (0-180)
J-l
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