Date   : Thu, 17 Nov 2005 12:19:29 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Best Emulator??

On Thu, 2005-11-17 at 02:28 +0000, Richard Gellman wrote:
> Jonathan Graham Harston wrote: 
> > > Message-ID: <20051116081723.25311.qmail@...>
> > >     
> > 
> >   
> > > > I would just like to clarify that BeebEm does support
> > > > IDE Hard Drive emulation.
> > > >       
> >     ^^^
> >   
> > > But not standard ADFS hard drive emulation.
> > >     
> > 
> > You mean, does not support *scsi* hard drive emulation.
> >  
> > But can do, just by somebody writing the relevant scsi.c and
> > scsi.h modules.
> >  
> >   
> I wrote these as part of my work on the Leeds university domesday
> emulator. It has a few things hacked into it (like video commands) but
> they are easily removed. It also needs either the data register read
> or write operation (can't remember which) modified to invert the bits,
> as the SCSI "adapter" in the domesday box used a different chip for
> one of the data register buffers to that on the hard drive SCSI
> adapter.

This purely on the Master? I seem to recall the BBC B SCSI board being
significantly more complex than the Master one, or at least in terms of
chip count.

I suppose it's possible they used 4 bit registers and buffers everywhere
in the BBC B one which is why the chip count's so high! I've always
meant to look at the schematic as I've never figured out why it's so
complex.

I believe that the SCSI controller in the Viglen BBCs is different yet
again, plus of course Torch made both a SASI and SCSI controller for the
BBC... so there's at least 5 different flavours out there!

cheers

Jules