> > If there's no support for a system, a kernel won't run on it (for very
> > long at least; it'll print out a message that the system is
> > unsupported, then halt).  You can't really do much more than that.
> > "Support" for a system includes all of the low-level code which
> > controls how it's I/O bus is attached, how interrupts are configured,
> > how the console is configured, etc.
> 
> But are all machines completely different in this respect, or is there
> some common ground? I have not studied this subject, mind you, but I'm
> just curious.

I've yet to see a machine with a one systype that was "sufficiently
close" to any machine of another systype that the same code would come
close to functioning correctly on it.  (Where "close to functioning
correctly" means "gets as far as finishing autoconfig or to a single
user prompt.")

Some parts of the code are in fact the same, e.g. all machines with
2117[12] chipsets can use the same 'cia' code, etc.  However, even
among workstation models, the interrupt glue in particular seems very
prone to change from machine to machine.  The different families of
server machines seem to consistently have different I/O busses, too.


chris