> > > Did you mark irq 9 a 'used by isa' in the BIOS ?
> > 
> > My machine is too old for that (it's a 486, incidentally). I have no
> > plug and pray, and there's no way to mark irq's as "used by isa" in my
> > BIOS. So I don't think that's the problem. Am I confused?
> 
> There's no PCI in this machine ?
> Then it's something else. Can you try another irq ?
> This could help determine if it's just irq 9 which has a problem.

Aha! I had misunderstood, and I didn't realize until now that PCI was
doing some funny IRQ allocation behind my back. With the help of your
message and a few others in private e-mail, my problem is solved. The
characters of the reply I'm typing right now are coming to you through
IRQ9 on my machine!

Thanks very much to all who helped out!

	-- Robert