Retrocomputing Stack Exchange is a question and answer site for vintage-computer hobbyists interested in restoring, preserving, and using the classic computer and gaming systems of yesteryear. It only takes a minute to sign up.
Sign up to join this community
The bus used for DEC's LSI-11 microcomputer implementation of the PDP-11 was originally and prosaically referred to as the LSI-11 bus, but thereafter it was universally referred to as the Q-bus.
Does this name have any meaning? And if so, what was it?
The LSI-11 Bus Specification has a section on history and folklore, and states
The original backplane to implement the LSI-11 Bus was designed to accommodate Digital's quad and dual height modules. It became known as the "Q-Bus" to reflect the quad board form factor. Both LSI-11 Bus and Q-BUS are Digital trademarks, but are not registered trademarks. Several bus architecture features of the LSI-11 Bus are protected by claims in Digital Unibus patent numbers 3,710,324 and 3,815,099. Some publications may also use the term SUB-UNIBUS, although this is not recommended.
When the LSI-11 Bus was expanded to provide 22 address lines, the terms Q22-Bus and extended LSI-11 Bus were adopted to specify backplanes [of] that bus [with] the four additional lines.
