>>>   A recent change to the tty line discipline has broken the pmax graphics
>>> console.  Serial console still works, which is one work-around.
>
> try this one...
>
> Index: sys/arch/pmax/dev/rcons.c
> ===================================================================
> RCS file: /rst/nb-cvs/syssrc/sys/arch/pmax/dev/rcons.c,v
> retrieving revision 1.45
> diff -u -u -r1.45 rcons.c
> --- rcons.c     2000/11/03 15:01:10     1.45
> +++ rcons.c     2000/11/05 20:52:31
> @@ -250,6 +250,8 @@
>         clalloc(&tp->t_canq, 1024, 1);
>        /* output queue doesn't need quoting */
>        clalloc(&tp->t_outq, 1024, 0);
> +      /* Set default line discipline. */
> +      tp->t_linesw = linesw[0];

The losssage is such a deep root in which pmax rcons uses a global
array struct tty rcons_tty[NRASTERCONSOLE] instead of ttymalloc().  In
retropect, the attempt to have psuedo-device rasterconsole/fb has
never been successful, and graphics console should be replaced with
wscons in favour of consistent approach and implementation.

Tohru Nishimura