BBC Micro - assemblers - info needed

From: Rob O'Donnell <>
Date: Wed Jan 22 14:44:00 2003

At 12:45 22/01/2003 -0500, you wrote:
> > On Jan 18, 16:16, Philip Pemberton wrote:
> >
> > > Finally, does anyone know how some discs were formatted so they were
> > > compatible with 40-track and 80-track disc drives?
> > The way Acorn did that with things like the Master 128 Welcome Disc was to
> > make all the directory entries (on track 0) point to tracks between 5 and
> > 9, and 20 and 39. Track 20 on a 48-tpi drive is where track 40 would be on
> > a 96-tpi drive:
>One has to be very careful with the formatting - there where several
>FS formats - some with varying compatibility. (Talking about the file system
>side here) The Master welcome disc used ADFS which was slightly more advanced
>than the more common DFS that was used on the earlier Acorns.
>I do have some scribbled documents which describe Acorn DFS in enough detail,
>plus some sample code which will extract and create disc images which I can
>send on (IIRC the code is actually on the web on one of the Acorn web
>sites - I
>can't remember which one though!)

 From what I recall from doing it many years ago, one could achieve a (low
capacity) dual-format disc by formatting and copying the files over on a 40
track drive, then putting the disc in an 80 track drive, and formatting *as
40 tracks* (so that it only did the first 40) and copying over the same files
in the same order. Oh, you had to copy over a suitably sized dummy file first
on each occasion (to skip the first half of the 40-track disc).

does that make sense?
Received on Wed Jan 22 2003 - 14:44:00 GMT

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