Re: can DOS 3.3 sector be larger than 256 bytes?

[92sabj@eng.cam.ac.uk (S.A.B. Jones)]

In article <37uk48$5it@aplcomm.jhuapl.edu>,
Robert Jensen  <jensen@aplcomm.jhuapl.edu> wrote:
>There are two bytes in the DOS 3.3 volume table of contents that
>hold the number of bytes per sector.  Does DOS 3.3 use this value
>for anything, or does it just assume 256 bytes per sector?  Is that
>part of the VTOC just there for compatibility with some never
>realized upgrade?

There is no effect on changing that byte in the VTOC... try it and see.
I don't actually know if it was intended as an upgradable feature or just
information, but it's not used.

It is actually possible to create a sector larger than 256 bytes, but that
requires your own disk-reading program because DOS cannot handle it without
a substantial patch. Choplifter, for example, used I think 5 tracks, and
each track was one continuous sector to speed up loading. I could go into
technical details if you want, but I won't here and now.

>I created a DOS partition on a SCSI disk and I would use 512 byte
>sectors if this is possible.  I could create a larger DOS disk that
>way.  I patched into the RWTS routine and everything works just
>fine, but I am only using 256 bytes of every SCSI block. (I have
>a II+ and still use a Merlin assembler that predates ProDOS.)

I'd be surprised if you could for the above reason: the patch to DOS would
be difficult (although theoretically possible). DOS is geared towards
writing 256 byte sectors, and allocates its disk space and so on accordingly.


   Stephen Jones
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92sabj@eng.cam.ac.uk