What is "q-bus"

The Q-bus (also known as the LSI-11 Bus) is one of several bus technologies used with PDP and MicroVAX computer systems previously manufactured by the Digital Equipment Corporation of Maynard, Massachusetts.

The Q-bus is a less expensive version of Unibus using multiplexing so that address and data signals shared the same wires. This allows both a physically smaller and less-expensive implementation of essentially the same functionality.

Over time, the physical address range of the Q-bus was expanded from 16 to 18 and then 22 bits. Block transfer modes were also added to the Q-bus.