Date   : Wed, 24 Jun 2009 11:12:46 +0100
From   : philb@... (Phil Blundell)
Subject: reading data from old hard disk

The easiest way of migrating the data would almost certainly have been
to just copy it over the network with multicopy.  The "400 floppies"
route wouldn't have worked very well since there is no floppy controller
on the HDFS.  If there had been, though, this wouldn't be an impossible
route: you'd only need 25 floppies to archive the contents of the HDFS,
even if it was completely full, leaving you with 375 to use for other
things :-)

I think there were few enough HDFSs built that it probably wouldn't have
seemed worthwhile to spend too much effort on making the MDFS be
backwards-compatible with their disks or tapes.  But that's just
speculation and it's possible that the MDFS SCSI interface is in fact
capable of driving the appropriate bridge boards to control an HDFS
disk.

I guess it's also worth mentioning that I don't actually know for sure
that the HDFS did use 256-byte sectors.  I'm assuming it did because
that seems to have been the common format at the time, and the M2235
datasheet gives the standard geometry as 32 sectors of 256 bytes each,
but I guess there is no particular reason why the disks couldn't have
been reformatted to 512-byte sectors for HDFS use.

p.

On Wed, 2009-06-24 at 10:33 +0100, Ian Wolstenholme wrote:
> There's nothing in the MDFS manual about compatibility with the FDFS/HDFS
> but I'd be a bit surprised if there wasn't a way of doing it somehow.  I
> can't really think that SJ Research didn't have a way of importing data on
> HDFS discs if you upgraded to an MDFS, apart from archiving it to 400
> floppy discs and restoring it to the new system!
> 
> Like you say, though, the MDFS does use 512 byte sectors and it appears
> that the HDFS uses 256 byte sectors.  That would make it easier to read it
> on a Beeb though with a host adapter and a bridge board like an Adaptec
> or Xebec one.  The data won't be an ADFS filesystem but you ought to
> be able to read off sectors with the OSWORD calls.
> 
> Best wishes,
> 
> 
> Ian
> 
> ----- Original Message -----
> From: Phil Blundell [mailto:philb@...]
> To: bbcmailinglist@...
> Cc: bbc-micro@...
> Sent: Tue, 23 Jun 2009 23:32:05 +0100
> Subject: Re: [BBC-Micro] reading data from old hard disk
> 
> On Tue, 2009-06-23 at 22:55 +0100, Ian Wolstenholme wrote:
> > If it's from an HDFS, can it not be connected up to the MDFS somehow?
> 
> Not easily, I don't think.  
> 
> The M2235 disk uses an ST-506 interface and is presumably formatted with
> 256-byte sectors since this is what its documentation seems to assume.
> The MDFS uses a SCSI interface and, I think, expects 512-byte sectors.
> 
> Even leaving aside the sector size problem, you'd need to find a bridge
> board that would interface ST-506 to SCSI (not SASI) and that was
> completely transparent, without needing the host to send any special
> initialisation sequence.  I'm not sure if such things exist or not.
> 
> p.
> 
> 
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