Something is slightly flakey with the console attachment on my Ultra10.
The keyboard probes like this:
   com0 at ebus0 addr 3083f8-3083ff ipl 41: ns16550a, working fifo
   com0: console
   kbd0 at com0 (console input)

And pcons doesn't attach:
   pcons at mainbus0 not configured

During the boot process, the "ipl 41" on the com0 attach line is the
last thing output, until /sbin/init starts /etc/rc.  If I boot single user
the keyboard eventually flakes out, where keys repeat, or I type a command
and hit enter and need to keep hitting keys to "flush" the keyboard buffer
or something.

Looking at com_ebus.c it appears that com_ebus_isconsole() returns true 
if com0 is stdin _or_ stdout.  Shouldn't it need to be both before it is
considered the "console" device?
I ask because in pcons.c pconsmatch() has the following:
        /* Only attach if no other console has attached. */
	return ((strcmp("pcons", ma->ma_name) == 0) &&
		(cn_tab->cn_getc == prom_cngetc));

This always returns zero on my Ultra10.  My assumption is the com0 attachment
is hosing this, but?

-Andrew