Strange third party board in PDP-11/45

Paul Birkel pbirkel at
Mon Jul 23 02:42:12 CDT 2018

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at] On Behalf Of Mattis Lind via cctalk
Sent: Monday, July 23, 2018 2:36 AM
To: Noel Chiappa; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Strange third party board in PDP-11/45

Here is how it is connected:

The sandwiched dual boards are i sitting in 27 / 26 AB. The board in 27AB
was empty (quick glance), while the board in 26AB has a few TTL chips on it.
 Slot 26AB is the Unibus A slot, Slot 27 AB should be a terminator on
Unibus B. (maybe there were terminating resistors on the second board.
Didn't check in detail) Slot 28AB is Unibus B and goes to the DD11-C and
the RK11-D backplanes.

The hex ABLE/ ACT board sits in slot 21 which is the memory controller
board for the MS11.

It very much looks like it is a Cache board. But why have some one written
"Not used" (Används ej) on it? I'll hope I find the documentation for it!



I wonder whether this CACHE/45 can coexist with MS11 memory on the Fastbus itself, or is designed to _replace_ MS11 memory by accelerating access to Unibus-based memory?  The available product literature doesn't clarify either way.


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