Plessey/Dilog DCV54

Warner Losh imp at
Sun Feb 14 16:39:14 CST 2021

On Sun, Feb 14, 2021 at 1:36 PM Paul Koning via cctalk <
cctalk at> wrote:

> > On Feb 14, 2021, at 3:30 PM, Nigel Johnson via cctalk <
> cctalk at> wrote:
> >
> > Has anybody got a DCV54 that they are using?
> >
> > I am trying to get one working with David Gasswein's mfm board and
> > having no luck.
> >
> > The controller is working fine with a standard floppy as an RX33, even
> > boots the MicroVAX from it.  But on-board diagnostics cannot format or
> > even recognise the mfm board as a winchester.
> >
> > Just got the scope out today and found that the drive select lines are
> > being terminated OK on the mfm board, bit the controller is not even
> > dropping drive select. (Yes I have tried new cables)
> >
> > Problem is I don't have anything old enough to test the mfm boards with
> > other than the Plessey controlelr!
> >
> > I'm thinking there must be some on-board config that I am missing on the
> > controller. - It has never had a real mfm drive connected to it.
> >
> > Any help appreciated,
> >
> > Nigel
> I had good luck with mine, though admittedly I have the advantage of
> having real drives to compare with (that's on a DEC Pro).
> Do you have the matching drive select jumper in place?  Can you see the
> "selected" signal being asserted by the board?
> Just to be sure... remember that floppy cables and hard drive cables look
> similar but are different and not interchangeable.

The two things I've been bitten by are making sure that dual cables have
the drive before the extra bit with the twist.

The other thing I've been bitten by isn't relevant here: I had the 20-pin
cable plugged into the wrong socket a few times when trying to image


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