Date   : Wed, 31 Oct 2001 05:43:04 -0800 (PST)
From   : Thomas Harte <t.harte@...>
Subject: Re: IDE interface for the beeb

>  My idea was not to implement a new drive type, but to build a circuit
which
>  emulated a floppy drive, accessing disk images on the hard-disk. The
control
>  panel would contain a selector to pick which disk image to read/write.

If it is of any relevance, it would probably be much easier to emulate the
floppy drive controller than the floppy drive, since SSD/DSD/etc images are
stored with that direct implication in mind. The 8271 requires only a much
higher level understanding of disc layout to emulate, so all DFS ROMs are
very easy to fool. Correct emulation of the 1770 is a much harder task, but
you can get away with considering it just to be a mildly more flexible 8271
for the purposes of fooling most of the ADFS ROMs. In addition to being able
to take SSD/DSD/etc at face value, timing is significantly less of an issue.

I was half considering a similar-ish project in the form of a new filing
system which reads and writes DOS format floppies (via any standard 1770
expansion), but on the side allows you to mount disc images on those
floppies. Any chance of something like that rather than a hard to construct
front panel?

-Thomas





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