Strange third party board in PDP-11/45

Paul Birkel pbirkel at
Mon Jul 23 23:57:21 CDT 2018

-----Original Message-----
From: Paul Birkel [mailto:pbirkel at] 
Sent: Monday, July 23, 2018 2:36 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: Strange third party board in PDP-11/45


>From the ABLE marketing literature:

CACHE/ 45 (CACHE BUFFER MEMORY) INSTALLS IN: PDP-11/45, -11/50 and -11/55
CAPACITY: 2048 byte (1 K word).
ENHANCEMENT FACTOR: Run time reductions to 50% (100% speed improvement) are
CACHE PARITY: Automatically goes off-line in event of any data error.
RANGE SELECTION: User may optimize hit ratio by upper/lower limit switch
SPECIAL FEATURE: Cache/ 45 can be enabled via software or console switches.

Presumably that's what Mattis has in-hand.


Computerworld, Page 23, July 26, 1976

ACT Has PDP-11/45 Buffer
SANTA ANA, Calif. - Able Computer Technology (ACT) has a 2K-byte cache
buffer for use with the Digital Equipment Corp. POP-11/45.
The Cache/45 is contained on a single printed circuit board that plugs into
system's chassis.
Buffer control is provided over every core memory address location on the
Unibus. A switch within the memory buffer permits a choice of either on-line
or off-line operation, the company said.
The buffer costs $7 ,000. ACT is at I 538-E Chestnut St., Santa Ana, Calif.

(Somewhat strange use of the expressions "on-line" and "off-line" operation,

I presume that the reason for "single printed circuit board" is that only a
single "normal" slot is occupied.


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