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Path: utzoo!linus!philabs!cmcl2!seismo!mcvax!enea!tut!jv
From: jv@tut.UUCP (Jukka Vanhala)
Newsgroups: net.micro.68k
Subject: Re: Call for 68K architectural change evaluations
Message-ID: <186@tut.UUCP>
Date: Wed, 29-May-85 11:20:58 EDT
Article-I.D.: tut.186
Posted: Wed May 29 11:20:58 1985
Date-Received: Sat, 1-Jun-85 13:42:41 EDT
References: <415@oakhill.UUCP> <boring.6412>
Reply-To: jv@tut.UUCP (Jukka Vanhala)
Organization: Tampere Univ. of Technology, Finland
Lines: 30

In article <boring.6412> jack@boring.UUCP (Jack Jansen) writes:
>
>... although there are undoubtedly *some* people who
>used the function codes for some unimaginable weird purpose who
>will be angry.
>What I wonder is: where would you use it for?
>

I'm working on a 68k do-it-yourself-PC and the reasoning behind
using function codes is simply:

- restart vector resides in supervisor code space => it must be
  burned on PROM (with a very simple monitor program)
- other exception vectors reside in supervisor data space and
  they must be writable (because I'm going to load the operating
  system from host) => they must be on RAM
=> so, at least supervisor spaces must be separated

Nothing prevents from mapping supervisor data space and both
user spaces onto physically same memory.

Anyway, I have a 68k chip already, so you can make whatever changes
you like :-O

jv (Jukka Vanhala)

Tampere University of Technology
Computer Science Laboratory
P.O. BOX 527 Tampere, FINLAND