Hello:

(But first some definitions:

Stacks:
	KS - kernel stack - a per-user-thread stack in the kernel address space
	IS - interrupt stack - a single stack for handling all interrupts

Yes, sure. But as I understand, there are machines which don't use a
seperate IS at all. Chris Hopps told that to Daniel Widenfalk on
amiga-dev a while ago (discussing possible problems to solve for a 060
port - hope it's still that way, at least I didn't yet find other
evidence in the source). We don't use it on NetBSD-Amiga, maybe not at any
other NetBSD/m68k (I assume that because -Amiga was derived from
-hp300, and all others where, mostly, derived from -Amiga and -hp300).

Thats a good think from an NetBSD-68060 port writers view, because the
060 doesn't even have a hardware IP at all (you can, however, simulate
it in software if you *REALLY* care (as in: you have reasons beyond my
knowledge, or you get paid for it only if you use it), because the
state bit switching between the IP/KP (in your terminology) is still
reset the same way, on interrupts, as on the '040, you just would have
to check it and change the stack yourself.

On the other hand, at least the VAX has one, in hardware, and you cant
avoid using it. (It has, btw, 4 levels of per-user SP, that is you can
create 4 protection levels... they were called user, supervisor,
executive, kernel).

Is there any reason we would generally need a seperate IP any time
soon? 

Regards,
	Ignatios Souvatzis