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(fdutils.info)Mixed size sectors


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Mixed sector size (MSS) formats
===============================

   Using larger sectors has the disadvantage that the granularity is
larger.  For example, when using 4096 byte sectors, there is enough
space to fit two sectors in a track of 12450 bytes raw capacity, but not
three.  However, the two sector format leaves plenty of space available
(4132 bytes), in which smaller sectors would fit.  For example, these
4142 raw bytes can be put to good use by filling them with a 2 KB sector
(2048+62), plus an 1 KB sector (1024+62) and a 512 byte sector, leaving
still 362 bytes for gaps.

   Mixed sector size formats take advantage of this by using sectors of
several different sizes on a same track.  This way, a maximum capacity
of 12KB per track, distributed in one 8k sector and one 4k sector can be
achieved.

   *Usage:* There is no known MS-DOS utility which can read basic MSS
disks.  Lilo is not yet able to boot from this kind of disks.

   *Performance:* As any format with larger sectors, the performance
for small reads and writes is worse due to the larger granularity.

   *Interesting Formats:*

     density     tot. cap.    throughput    media description
     3 1/2 DD     880KB        28KB/s       hd tracksize=11b mss
     5 1/4 HD    1600KB        30KB/s       hd tracksize=10KB mss
     3 1/2 DD     880KB        28KB/s       hd tracksize=11b mss
     3 1/2 HD    1840KB        28KB/s       hd tracksize=23b mss
     3 1/2 HD    1920KB        30KB/s       hd tracksize=12KB mss
     3 1/2 ED    3680KB        56KB/s       ed tracksize=23KB mss
     3 1/2 ED    3840KB        60KB/s       ed tracksize=24KB mss

   For MSS formats, the system figures out the most efficient
repartition of sector sizes by itself.  You do not need to describe the
number of sectors and their size.  For MSS disks, the capacity of one
track is described directly, using the `tracksize' parameter.

   The `1920KB' and `3840KB' formats may be unreliable on some
computers.


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