When I didn't have the 'flags 1' argument in my config.new style config
   file, the serial line to my modem (which is on the 3rd port of the
   4-port card) would not work properly--anything which tried to talk to it
   would wait on ttyoutput.

Oops!  You're right; without that the com driver sets MCR_IENABLE,
which puts the AST board in `one IRQ per port' mode, but is required
for the RT card.

I just updated the config files.