VAX 11/730 modules

From: Ethan Dicks <erd_at_infinet.com>
Date: Fri Jul 10 09:49:30 1998

> AFAIK all DEC unibus peripheral controllers work here.

There *might* be an ancient SPC that doesn't, but yes, all DEC cards
I've ever seen work in a MUD slot.

> Here's what's going on.
>
> On an original Unibus slot, connectors A,B were either Unibus In/Out...
>
> C-F were not changed AFAIK on any slots.

AFAIK, that is all correct.
 
> On a MUD slot, there were memory signals on connectors A,B. Originally
> these were just the Unibus address and data lines, wired almost the same
> as a Unibus In or Out connector. However some grounded pins on the Unibus
> connector were assigned to extra power lines (battery backed, etc) on the
> MUD slot, so plugging a terminator or Unibus cable into an MUD slot
> shorts out the PSU. Bad idea.

Right. Some bozo vendor shipped me a 11/725 (11/730 CPU, different case)
with no grant cards and the terminator in a MUD slot. Stupid me turned on
the power without checking the cards. Stupid vendor did replace the PSU.

> For this reason no peripheral card should ever do anything but take power
> from A and B unless you know exactly what you are doing.

True, but that third-party board I used to make was designed by Real
Engineers (tm). They just *knew* that the Unibus signals were on A and B
and didn't worry about those C and D fingers. You should see the mod
to make that board work in a MUD slot - bunches of wires.

> > What ever you do, don't install the M9202 terminator in a higher slot than
>
> THe M9202 is a bus jumper, isn't it? The terminator is the M9302.

Doh! You are correct. And the M9312 should be the boot strap/terminator
for the 11/34 etc, IIRC.

-ethan
Received on Fri Jul 10 1998 - 09:49:30 BST