DECmate II Questions

[Warner Losh]

On Sat, Apr 2, 2016 at 11:49 AM, Paul Koning <paulkoning at comcast.net> wrote:

>
> > On Apr 2, 2016, at 1:27 PM, Robert Jarratt <robert.jarratt at ntlworld.com>
> wrote:
> >
> > I have been looking at my DECmate II recently. I got an Italian version
> of
> > WPS 1.0 for it and that works fine, except that I don't have an Italian
> > keyboard so finding some of the characters is a bit tricky. :)
> > ...
> > Any recommendations for how best to image RX50 diskettes? I want to
> preserve
> > the diskettes I have.
>
> Are they the same format (80 tracks, 10 sectors, 512 bytes) as the RX50 on
> PDP11s?  If yes, you can either use a PDP11, or you can configure Linux to
> 10 sector per track format and use dd.  If the sector ordering is as
> strange as on the PDP11, dd will get the data very much out of order, but
> it should all be there.  I can find the PDP11 interleave rules if you need
> them.
>

They are similar to the PDP-11 layout, with special rules for tracks 0, 1
and 79 IIRC. So long as
you are using a compatible floppy drive, you'll be able to read / write
them. I've connected my
RX-50 from my DEC Rainbow 100B to a PC controller in the past with some
luck in reading
writing the disks (raw mode only). I've also had good luck with the TEAC
55F. Other models, like
ones in IBM PC AT and newer that do 1.2 MB have 'issues' creating readable
RX-50 disks.
DD certainly would be one way to image them. However, there's a caveat with
that. DD
will read the sectors labeled 1, 2, 3, ... 10 in that order. However, if
you read the entire track
off the disk you'll find they are stored in 1 6 2 7 3 8 4 9 5 10 order
(again, IIRC, the order is
different, but might not be this exactly). Back in the day, people (not me)
reported success of
duplicating via dd, only to find that the performance really sucked. My
brain can't recall if
this was on the PDP-11 / Professional formatted disks, or on the DECmate II
disks.

Wish I could be more helpful.  Here's a link that has all the details that
my brain is likely
recalling wrong:

http://www.ibiblio.org/pub/academic/computer-science/history/pdp-8/docs/rx50faq.doc


Warner