Quake on plan 9

[rob@plan9.att.com rob@plan9.att.com]

You'll need to do some minor system hacking to give you up/down
events on the keyboard.  Plan 9 hides all that stuff for you as a service
to most software, so on machines that have up/down events (the
first few machines we ported to didn't) we generate UTF directly.
It would be a few minutes' work to make another device file that
gives you the up/down stuff in any form that's helpful.  Similar
comments apply to the mouse.  With a little more work, this could
even be made to work through the window system.

The framebuffer is mappable already, although you may need to
add a line to a table in the kernel and recompile before you can
get to it.  If you're on a VGA, you may also need a hook to get to
the routine that copies from the internal buffer to the page-mapped
display.  This is easy, too, although getting it to cooperate with the
window system is not.  (It's very easy in Brazil, but that's another
story.)

There is a sound driver for the Sound-Blaster cards and Nextstations.
I don't know it well enough to say if it does enough, but as you say
it's a straightforward project if not.

Again, unbuffered TCP/IP will take a little kernel work but not much.

-rob