Date   : Sat, 22 Oct 2005 22:23:01 +0100 (BST)
From   : Greg Cook <debounce@...>
Subject: Re: Programming the 8271 and 1770 FDC's from BASIC

On 20 Oct 2005 00:57:21 +0100, Jonathan Graham Harston
<jgh@...> wrote:

> > Message-ID: <5C1EE813AA8F46A88588FF7C284069B1.MAI@...>
>  
> "Ian Wolstenholme" <BBCMailingList@...> wrote:
> > > It's here: http://www.8bs.com/aumags27.htm
> > 
> > Splendid - is there a similar feature on the 1770?
>  
> Well, as the article is actually "accessing disks with OSWORD
> &7F", regardless of what the title claims it is, the exact same
> code will work with the 1770 controller. That's the whole point of
> having APIs.

The listing should work happily for SD discs, and DD if the destination
disc has been pre-formatted, and the PROCformat call is removed.  (That
is, under sane DFSs that retry failed commands in both densities.)  

Formatting custom double density discs typically won't mean writing a
1770 driver; the more conscientious DFS will provide full functionality
in command &63 for its own use.

The problem is how to communicate which density to use -- an argument
to *FORMAT normally provides it, so users of OSWORD &7F must do an
extra command or sometimes a poke to set the density.  As usual, a
disassembly and/or debugging session will show how to get the quickest
'result', but in any case DD formatting won't be 'portable.'

Greg Cook
debounce@...
http://homepages.tesco.net/~rainstorm/



       
       
               
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