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NEC CP/M-86 User Manual

NEC CP/M-86
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BIOS
Disk Definition Tables
The values
of
BSH
and
BLM
determine
(implicitly) the
data
allocation
size BLS,
which is
not
an
entry
in the disk
parameter
block. Given
that
you
have selected a
value
for
BLS,
the
values
of
BSH
and
BLM
are
shown
in Table 7-4, where all values
are in decimal.
Table 7-4
BSH
and
BLM
Values for Selected
BLS
BLS
BSH
BLM
1,024
3
7
2,048 4
15
4,096
5
31
8,192
6
63
16,384 7
127
The
value
of
EXM
depends
on
both
the
value
of
BLS
and
whether
the
DSM
value is
less
than
256
or
greater
than
255, as
shown
in Table 7-5.
Table 7-5 Maximum EXM Values
BLS
DSM
< 256
DSM
> 255
1,024
°
N/A
2,048 I
°
4,096
3
1
8,192 7 3
16,384
15
7
The
value
of
DSM
is
the
maximum
data
block
number
supported
by
this
particular
drive,
measured
in BLS units.
The
product
BLS x (DSM+I)
is
the
total
number
of
bytes held
by
the
drive
and,
of
course,
must
be
within the capacity
of
the physical
disk,
not
counting
the reserved
operating
system tracks.
The
DRM
entry
is
one
less
than
the
total
number
of
directory entries, which
can
take
on
a 16-bit value.
The values
of
ALO
and
ALl are
determined
by
DRM.
The two values
ALO
and
ALl
can
together
be considered a string
of
16-bits, as shown below.
ALO
ALl
15
7-5

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NEC CP/M-86 Specifications

General IconGeneral
BrandNEC
ModelCP/M-86
CategoryDesktop
LanguageEnglish

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