Commodore Amiga A500 Technical Reference Manual page 187

These numbers can be from
00
to 1 0 (hex), or 1 7 sectors per track
or any number that the host wishes to specify that meets the drive
track capacity. Bad block marks are shown for sector numbers 1 and
4
in all four interleave factors illustrated. The other requirement of
the host is to provide the logical sector number. Using this scheme.
sectors can be recorded in any interleave factor desired. Byte four of
the command block then specifies the number of sectors to be for-
matted per track. Also the host is free to choose marking individual
sectors or entire tracks bad.
A t
the end of a track format, the host
can re-issue the command, for formatting the track across head
boundaries as shown below:
Table 5-8: Interleaving Across Head Boundaries
Using the above spiral format approach, the HDC has approximately
1
mS for any processing overhead required. This
1
mS loss in the 1
:l
performance across head boundaries, assuming a disk rotational
speed of
3600
r.p.m. is reasonable. Across cylinder boundaries, the
1
:l
interleave factor cannot be maintained because of the step rates
involved. To format the entire disk using the Format Track com-
mand the host must update the buffer, if desired, and re-issue the
command every track formatted. This is not really a major advantage
since the host driver routines can easily re-issue the command in a
loop until the entire disk is formatted. This gives the host total flexi-
bility to format the drive using any clever algorithms for formats
across head and cylinder boundaries instead of a canned approach.
TTack Format The data fields are filled with FF hex, and the
ECC
is generated as
specified by the related coding options. The Gap
3
value is deter-
mined by the drive motor speed variation, data sector length, and the
interleave factor. The interleave factor is only important when 1
:l
interleave is used. The formula for determining the minimum Gap
3
is:
M
=
motor speed variation (e.g. .Ol for
+ /
-
1%)
S
=
sector length in bytes
K
=
1 8 for an interleave factor of 1
E
=
2 if
ECC
is enabled
V
=
number of overhead bytes required for the
HDC
between sectors
=
9
(for an interleave factor of 1
)