Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdcad!ames!sdcsvax!ucsdhub!hp-sdd!hplabs!hpcea!hpfcdc!hpfcrj!bayes
From: bayes@hpfcrj.HP.COM (Scott Bayes)
Newsgroups: comp.sys.mac
Subject: Re: I've heard of disclaimers but this is ridiculous
Message-ID: <3940002@hpfcrj.HP.COM>
Date: 15 Dec 87 19:59:29 GMT
References: <7006@apple.UUCP>
Organization: HP/SSO Ft. Collins, CO.
Lines: 30

>The third paragraph of section 8.4 (page 8-22) in a current 680x0 
>manual states, and I quote, 
>
>	"The system software should not depend on a particular
>	 exception generating a particular stack frame. For compatibility 
>	 with future devices, the software should be able to handle 
>	 any type of stack frame for any type of exception."
>
>HELLO?? WHAT THE HELL DOES THAT MEAN????  
>Seems just a bit "too" general for me.  Isn't it a bit late in the game 
>to publish such a general disclaimer on the part now??!?!! Does this mean
>I have to go back and rewrite all the exception handlers I've ever
>written for the 680x0 parts and turn them into psychic AI modules?
>How can I write an exception handler and NOT depend on what the exception
>stack frame looks like?

I couldn't find the reference in my 68020 manual.  I'm guessing it means
you should check the frame format word, and from that you can find the
nature of the frame data.  I believe I remember hearing that the 68882,
for example, may generate a larger, different frame for the same
co-processor exception that the 68881 could generate.  We have a bit of
code that does something on the edge of assuming that a given exception
has a given frame; we'll have to turn the handler involved, should we
support the 68882.

Disclaimer: the opinion expressed above is my personal opinion, and does not
reflect an official position of Hewlett-Packard Co.

Scott Bayes
hpfcla!bayes