Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!cbmvax!ditto
From: ditto@cbmvax.UUCP (Michael "Ford" Ditto)
Newsgroups: comp.sys.att
Subject: Exception stack frames (Re: Could a 68881; HwNote07)
Summary: stack frames stay on the stack; only minor changes needed
Keywords: HwNote fpa 68881 UNIXpc hard-ware 7300 68020
Message-ID: <5113@cbmvax.UUCP>
Date: 26 Oct 88 23:32:55 GMT
Article-I.D.: cbmvax.5113
References: <372@uncle.UUCP> <5087@cbmvax.UUCP> <3731@rphroy.UUCP>
Reply-To: ditto@cbmvax.UUCP (Michael "Ford" Ditto)
Organization: Commodore Technology, West Chester, PA
Lines: 25

In article <3731@rphroy.UUCP> tkacik@rphroy.UUCP (Tom Tkacik) writes:
[ about replacing the 68010 with an 020 ]

> [ ... ]  The size of the saved state of a 68020 and 68881
>is much larger than that for the 68010.  Each time there is a context switch
>the OS thinks it is putting away info for the 68010.

The size doesn't matter, since the exception frame is never moved from
where it sits on the per-process supervisor stack; only the register
set is saved in the user area.  What is important, though, is the handling
of the new frame types.  This essentially means adding a few new cases
to the bus-error trap handler.

>  Perhaps
>the hooks are all there, only waiting to be found.  Any ideas about where
>to start looking?

I'm looking, I'll let you know what I find.
-- 
					-=] Ford [=-

"The number of Unix installations	(In Real Life:  Mike Ditto)
has grown to 10, with more expected."	ford@kenobi.cts.com
- The Unix Programmer's Manual,		...!sdcsvax!crash!elgar!ford
  2nd Edition, June, 1972.		ditto@cbmvax.commodore.com