Date   : Mon, 05 Jul 2004 22:58:49 +0200 (BST)
From   : Johan Heuseveldt <johan@...>
Subject: Re: Acorn Winchester unit

Hi all,

On Mon 05 Jul, Mark Usher wrote:

> There are usually parameters in one of the command blocks on the SCSI unit
> that you can set to the sector size. Just look at the SCSI spec, I can't
> remember off hand just at the mo which one. Usually drive specs will tell
> you if the drive has the capability or not, most of the older SCSI-1 drives
> do.

And others seem - I feel - to be optimistic too, for connecting a SCSI
drive directly to the Host-Adapter, and let it work with ADFS.

I don't want to spoil everyones appetite, but generally speaking this
is /not/ possible.

Why? Because SCSI drives won't allow a low level format, and there is
no way to use a logical model of 256 bytes sector on top of the physical
512 bytes per sectors /in/ the drive.
But you can do that in software of course!
But you should write something yourself though, as it is not easy
to patch ADFS: recalculate blocknumbers, and handling 512 bytes
reads/write on low level before ADFS Filer is involved, which needs
extra memory/code.

If it was /that/ simple to connect a SCSI drive to the host adapter
directly, it would be widely in use for twenty years now! :-) I think
it's a bit pedantic to assume this is an easy task, which no one has
discoverd so far! :-) Hm, perhaps it's me who's pedantic now! :-|


Is this all? No it isn't, There are a few exceptions!

 1: Try to find the Seagate SCSI drive: ST157N (the 'N' is vital!)
 
     as this drive /does/ allow a low level reformat with the desperately
      needed 256 bytes per sector; it then fully works under ADFS!

 2: The (old) Syquest removable 44 MByte is also known for allowing a
     physical reformat to 256 bytes per sector.
    Not sure about the 88 MByte.


Another way is finding the original info about the -4000 board, as this is
quite intelligent. Perhaps a logical 256 bytes per sector is supported?

I know someone with those docs. I'll ask him to borrow those for scanning in.


I hope this is of some help to you all?
Johan



-- 
Johan Heuseveldt <johan@...              >
  aka  waarland

  The best place is a Riscy place
 
Rock journalism is people who can't write, interviewing people
who can't talk, for people who can't read. - Frank Zappa