Subject: Re: Floppy driver
To: None <>
From: Brad Pepers <>
List: amiga-dev
Date: 02/28/1994 18:01:37
<stuff gonzo!>
> No you can't treat an MS-DOS disk as you would an ADOS disk.  If my memory
> serves correct - and forgive me if it doesn't - we're going back at least 3
> years :-)  What I remember having to do was to turn on DMA on a sector by
> sector basis.  And I think that the WD chip writes a magic MFM word (DSKSYN
> byte) before each sector.  And I think that ADOS writes out even and odd
> bits to separate memory chunks (after you read in a track) but the WD chip
> does not -
> hence your blitter MFM encode/decode are radically different.  I also remember
> that I had to determine wheter the DMA to be started was indeed for the
> sector I wanted.  It would obviously help to get a DOS formatted floppy and
> examine it.

I think thats how it is done on the msdos machines but in their case the
WD chip does most of the work. On the amiga its harder to do and not
really worth the effort. Instead a whole track and a bit are read in
and passed to routines that deal with finding the sectors in the raw
data. This should work with MSDOS disks too (different sectordecoding
and something with the INDEX pulse on writing but mostly the same).

+----------------------------Ren & Stimpy--------------------------------+
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| loose the marmosets on us! Don't worry, little missy! I'll save you!"  |
+------------------ Brad Pepers -- -------------------+