More on PDP 11/24 (hints & Maintenance Card infos needed)

From: Ethan Dicks <>
Date: Mon Jan 3 19:16:29 2005

On Mon, 03 Jan 2005 16:23:53 +0100, Pierre Gebhardt <> wrote:
> Thanks alot for your advices and the links, Ethan.

You're welcome.
> > No. There are 1MB boards for the 11/24, but they are somewhat odd,
> > IIRC. I have an 11/24 at home with a KT24 (M7134?) Physical Address
> > eXtension (PAX) board... that lets you put more than 256K of memory in

> My 11/24 _uses_ the KT24 Mapping Module with the suggested MS11-PB,
> giving it 1MB of ECC Memory.


> I can guarantee, that this combination works :^)

It all sounds reasonable, but I hesitate to make absolute
pronouncements unless I can verify things myself.

> There's another board, I own: a MS11-LB (M7891-BB) with 128kb.
> But I suppose that it doesn't make much sense to put this one together with the
> MS11-PB. The Ms11-PB is certainly much faster than the MS11-LB.

Right, but what I don't remember is if you can use the MS11-PBs
_without_ the KT11. I am almost positive the KT11 is optional (I
remember buying my 11/24 in college for $300 + S&H, and the KT11 was
extra (and $300 as well, IIRC. I spent a _lot_ on trying to run UNIX
at home in the 1980s).

Mentioning the MS11-LB makes me wonder if it even works with the KT11
at all, or if it is designed to sit _on_ the Unibus for a 256K
machine. It's been 20 years since I reconfigured an 11/24. I only
ever messed with memory once, so I'd have to look everything up now.

> Unfortuantely, the National Semiconductor boards can't be used, they were built for a VAX 11/750...

> Currently, I have some problems to get this baby work.
> There is a strange malfunction: When typing in some letters or digits on the keyboard (VT420), the screen turns out some sort of random characters at the _at_-pormpt.
> It's very weird !
> Sometimes, when I turn it off and on to give it another try, it becomes impossible to type something.
> The prompt is waiting, the cursor's blinking and the machine try to bootstrap, when pushing the boot-button,
> but I simply can't type in anything !

Check your terminal settings vs what the CPU card wants. Check the
cable from the CPU to the outside world for, say, a bad ground wire
(could have gotten pinched). Check the terminal not in local mode,
but with a loopback connector (local mode doesn't exercise the line
drivers on the terminal). Try a PC or a different terminal instead of
that VT420. Check your backplane voltages, especially -15V to make
sure the CPU's line drivers are getting properly fed.

If _all_ of those tests fail to turn up something, there's a small
chance it's the UART on the CPU card, but I'd really doubt it's that
far upstream. Cables, settings, and voltages are common problems;
less common are blown line drivers, but it does happen.

Good luck,

Received on Mon Jan 03 2005 - 19:16:29 GMT

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