Date   : Thu, 20 Oct 2005 00:57:20 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: Programming the 8271 and 1770 FDC's from BASIC

Jules Richardson <julesrichardsonuk@...> wrote:
> I *think* xfer makes use of fairly high-level ROM routines to read/write 
>   at the track level though (not studied the code yet), whereas I'd need 
> to presumably talk to the disk controller chip direct.
 
To access non-Acorn disks I would recommend a computer with a 1770
controller, ie a BBC Master or B/B+ with 1770. A lot of disk
formats out there are double density, even when they store less
data than a BBC disk.
 
I've used custom code on my Master to access 3" Amstrad, Einstein
and Spectrum disks. Some of these are 40 track single sided, and
only store 180K!
 
> Anyone out there have any useful notes or pointers to info? May well be 
> a non-viable project for all sorts of reasons, but it was just an idle 
> thought this morning...
 
As you will be effectively writing a disk driver as opposed to
accessing native format disks it is likely that you will have to
write custom NMI code to collect the disk data and will have to
play with the hardware directly. There are a few disks you can
trick OSWORD &7F and &72 into accessing, but it can be tricky.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
RISC OS Internationalisation - http://mdfs.net/Software/RISCOS