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(fdutils.info)Larger sectors

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Larger sectors
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   The floppy controller allows us to use larger sectors than the
default size of 512 bytes. All powers of two larger than 256 bytes are
acceptable sector sizes.  Large sectors have the same header and gap
sizes than smaller sectors, thus the overhead per byte of data is
smaller.  A little calculation shows this: A 1024 byte sector takes up
at least 1024+62+1 = 1087 raw bytes.  You can fit eleven sectors of this
size into a 12450 byte track.  This represents 11KB of data per track,
versus the 10.5KB only that can be achieved with 512 byte sectors.

   *Usage:* MS-DOS and other operating systems cannot normally read
these formats.  Lilo is not yet able to boot from this kind of disks.

   *Performance:* When any portion of one of these larger sectors is
read, the entire sector must be read.  When any portion of such a sector
is written to, the entire sector must be read, and then written back
with just the necessary portion modified.  Both of these circumstances
can entail worse performance than are listed in this table for small
reads and (especially) small writes.

   *Interesting Formats:*

     density     tot. cap.    throughput  media description
     5 1/4 HD    1440KB        30KB/s     dd sect=9 ssize=1KB
     3 1/2 HD    1760KB        55KB/s     hd sect=11 ssize=1KB
     3 1/2 ED    3520KB       110KB/s     ed sect=11 ssize=2KB

   The `ssize' parameter of the format description indicates the sector
size to be used.