Artifact Details


UNIBUS and ribbon cable

Catalog Number



Physical object


Digital Equipment Corporation (DEC)

Identifying Numbers

Other number 2 Handwritten on label on bottom
Other number BC11-A-04 Printed on display label
Other number M919B Etched on one bus connector
Other number M929B Etched on one bus connector
Part number 17-00286-00 On label on ribbon cable in case


overall: 13 in x 24 in x 11 in


This object consists of a UNIBUS cable and a ribbon cable.
Both were previously part of a display at TCM Boston, and the mount text read: "All of the members of the PDP-11 family of computers were built around an innovative approach to computer design called the UNIBUS. Before the UNIBUS, the central processor not only processed information, it continually monitored and controlled all the interactions between memory and I/O devices. With the UNIBUS, all components were connected, not to each other, but directly to a single, bidirectional bus. Each device had its own unique address and interrupt priority. The UNIBUS was the first single data bus able to send, receive , or exchange data without processor information. The new design not only improved performance by off-loading the CPU, it simplified system design. The UNIBUS provided a new level of "modularity" in computers. By defining an interface specification for each piece of the system, it allowed independent and parallel development of memory, peripheral and central processor. And because components were connected to the UNIBUS, not to each other, peripherals, memory, even processors, could be removed and replaced, or added later--without affecting the rest of the system. The UNIBUS made it possible to introduce the PDP-11/20 with a minimal hardware configuration and options to be added later. In April 1970, when the first two PDP-11/20's were delivered to customers, dozens of PDP-11 development projects were under way. From May to November, 17 new products for the PDP-11 were introduced. Options were developed at such a pace that it was not unusual for price lists to be out of date by the time they were printed."