Tandy 600 Programmer's Reference Manual page 167

INT 57h,
Function
8
-
Media Check
Entry
AH =
9 (function
code)
AL =
drive
number
CL=
media
descriptor byte
Exit:
AL = media
status
-1
=
media has been changed
=
don't
know
1
=
media has
not
been changed
The Media
Check
function
always
returns
which
means
the
Tandy 600 does
not
know
whether
the
media has been changed
or
not.
Therefore, the Build
BPB
function
is
called
frequently.
However,
this
is
not a
big
overhead
cost
because the
ROM-BIOS
only returns the
fixed
BPB
without
any
FDD
access. This
means
that
the
Tandy 600
only
can access
FDD
formatted
media
following
one
of
the
two standard
MS-DOS
formats.
The
other
standard
MS-
DOS
format
is
not
available.
However,
the disk
can be accessed by other
MS-DOS
machines
(i.e.
compatibility
must be resolved by the desk-top
MS-DOS
machine
—
not
by
the
Tandy
600).
The
disk format
is
one
of the
two
MS-DOS
standard formats.
Number
of
Tracks:
80
Sectors per Tracks:
9
Bytes per Sector:
512
Reserved
sectors:
1
Number
of
FATs:
2
Sectors per FAT:
2
Total
DIR
entries:
112
Sectors per DIR:
7
Sectors per
allocation
unit:
2
Media Descriptor Byte:
F8
Physical Format:
IBM
format
162