CP/M on the MZ-80K -
Disk Parameter Block & Bootstrap Code
written by Maurice Hawes / SUC/UK
Source: SUC-magazine July 2003, Volume 23 Number 2, p. 10
|Sharp Users Club - MZ-80K Section - CP/M via DPB.COM|
( Crystal CP/M, like most CP/M systems, uses 128-byte logical sectors )
16 Sectors per Track gives a track capacity of 128 * 16 = 2K - exactly the same as in MZ-80K Disk Basic. The SUC program DISKEDIT.K7 may therefore be used to examine a Crystal CP/M disk, and edit it if necessary.
In Crystal MZ-80K CP/M 2.2, each side of a 5.25" disk holds
35 'Logical Tracks'. A double-sided disk is therefore seen as 70 'Logical
Tracks' and the overall capacity of such a disk is
BSH = 3 and BLM = 7 both give a block size of 1K ( 1024 bytes )
EXM = 0 implies that, in this case, a 'Physical Extent' is the same as a 'Logical Extent' i.e. they are both 16K.
DSM = 129 implies that a disk contains 130 CP/M blocks ( i.e. 130K ):
DRM = 63 implies that the Directory can hold 64 entries.
AL0 - AL1 = 1100 0000 implies that the Directory is allocated the first 2 CP/M blocks ( i.e. Blocks 00 and 01, total 2K ).
OFS = 5 implies that the first CP/M block ( Block 00 ) is at
the start of Track 5, and that Tracks 0 - 4 are reserved for bootstrap
& system files.
FILES.COM in XTAL MZ-80K CP/M confirms this figure.
DISKEDIT reveals the following sections of code on Tracks 0-4:-
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