[HECnet] PDP Ignorance

[John Wilson]

From: "Steve Davidson" <jeep at scshome.net>

This is simple.   If the backplane has 2 slots per row then it is a QBUS
(/2 variant).   If it has 4 slots per row then it is also QBUS but could
be either 18-bit or 22-bit - the part number on the side of the
backplane will tell you for sure.   If the backplane has 6 slots per row
then it is UNIBUS.

In the wild this seems to be true, but the DDV11B (a hex-high Q-bus
backplane) existed at least in the minds of the handbook authors
(see p. 159 of Microcomputer Interfaces Handbook 1980).

John Wilson
D Bit