Multiplexed Special Devices

[Steven Bellovin]

As several people have noted, multiplexor devices date to v7.  They were
indeed quite buggy, though I know of a few uses for the 4.1bsd versions.
The early BSD support for BLIT terminals (the ancestor of the 5620 and
the 630) was based on them, as was the IPC mechanism for a multi-player
adventure-style game called t4c.

The driver had a lot of potential if only (a) it were better-documented,
and (b) it worked...