On Mon, Apr 27, 2009 at 11:05 AM,  <hwarin@neuf.fr> wrote:
> Thanks, Anders ....
>
>  I had a look at this Wikipedia article .....
>
>  That, I am certain that it's not "theorically" complex to add
>  numerous HDD to a 9090. How many ? 4 - May be 8 ... I won't try by
>  myself

It's not difficult to add two MFM drives to the SASI controller, IIRC,
but you wouldn't be able to add more drives than that without using a
different SASI board.  Back in the day, there were boards that talked
to MFM drives that could support up to 4 drives, but you'd have to
find a couple and then research their command and feature set.  They
would have to be completely command-level compatible with the SASI
board in the D90x0 (remember, pre-SCSI was _not_ standardized), or
you'd have to tweak on the firmware on the DOS board.

I don't think SASI supports multiple targets per bus like SCSI does
(or if it does, it doesn't do it in a compatible way), but if one were
to modify the DOS board to do "real" SCSI (which might take a little
hardware hacking plus firmware hacking), then one could "easily" add
up to 7 SCSI targets, which, if they happened to be 4-drive Adaptec
bridge-type cards, could allow you to address 28 spindles.  In
practice, this isn't feasible, but it gives you an idea of the maximum
extent possible.

What's more practical, I think, is to hack the DOS board to handle
SCSI, then in firmware, support multiple drive partitions using the
multiple-drive method from the dual floppies, "0:", "1:", etc.  One
spindle, but multiple drive numbers.  What I don' t know is possible
presently is if one would be able to easily copy files from "drive to
drive" as one does with a 4040 or 8050.  That might take additional
firmware work or just place the restriction that you have to use a
host-based file copier and move the data up and down the IEEE cable
rather than from drive to buffer and back to drive.

Of course, these days, D90x0 parts are so rare that it's probably more
practical to consider a 100%-new IEEE-488 "hard drive" that might use
FLASH rather than a real disk, but could use either.  Since there are
probably very few programs that use DOS 3.0 REL files with their
"Super Side Sectors", it would probably be sufficient to emulate the
behavior as needed to get directories and read and write ordinary
(SEQ, PRG) files.  I like the idea of hacking a real D9090, but only
because I already have one.  It's not like my efforts will be easy to
share since so few people have these drives.

-ethan


       Message was sent through the cbm-hackers mailing list