> I was hoping I could rehack the BSD OS to
> include only the stuff that I need and illiminate the stuff that depends
> on bios functions I haven't implemented, is this realistic?

Shouldn't be a problem. You can remove so many things from the kernel that
it practically becomes a task-switcher and IPC layer. Be warned that you
will probably want to retain a small root filesystem with an /etc directory
-- many common system facilities rely on configuration files in /etc.

Unix is only inappropriate for embedded if you have hard requirements for:
    - memory (under 4 megs)
    - deterministic interrupt response
    - deterministic process scheduling
    - avoiding the use of virtual memory

An embedded system is really just a complex and specialized server, and Unix
has lots of history & experience running more general servers such as file,
print, and database servers.

Todd Whitesel
toddpw @ best.com