Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!samsung!spool2.mu.edu!uunet!mcsun!ukc!strath-cs!cs.glasgow.ac.uk!bru-cc!eesrajm
From: eesrajm@cc.brunel.ac.uk (Andrew J Michael)
Newsgroups: comp.os.minix
Subject: Re: Where to start for 68010 port?
Summary: Use MINIX-ST
Message-ID: <1922@Terra.cc.brunel.ac.uk>
Date: 6 Jan 91 19:56:47 GMT
References: <1990Dec29.014903.12192@chance.UUCP>
Organization: Brunel University, Uxbridge, UK
Lines: 53

In article <1990Dec29.014903.12192@chance.UUCP>, john@chance.UUCP (John R. MacMillan) writes:
> 
> A friend and I are thinking of porting Minix to a spare AT&T
> UNIX PC that's lying around, and we wanted to know which port
> we should start with.
> 

(Stuff deleted)

> Is it worth starting from a 386 version
> for the memory protection, and 32-bit stuff, or should we start
> from a 68000 version and add on?  And if the latter, which one?
> We want the machine to boot Minix, not run it under the
> existing OS.
> 
> -- 
> John R. MacMillan       | I wish I had a nickname like Crusher, Snake or Dennis
> john@chance.UUCP        | Because guys with nicknames always get the gal.
> ...!scocan!chance!john  |       -- barenaked ladies


I'd strongly suggest using MINIX-ST as a starting point, because you can use
the existing ACK compiler to get a running system pretty quickly.  Use the
ST shadowing method until you have got something running, then try playing 
with the MMU on the AT&T box.  Trying to get it all working, MMU and all in
one go could be rather awkward.  (Anyway, I like the divide and conquer
approach personally !)

Your main problem will be finding a host machine to compile your new version
of MINIX in the first place.  If you can find an ST/Mac/Amiga lying around
then you should be OK.  If not, you will need to cross-compile with gcc on a
Sun or similar.  The problem here is that gcc won't compile the out-of-the-box
sources without some  modifications.

Regardless of the method used, beware the stack frame in kernel/stmpx.s at the
point where it is set up around label L5 (if I remember correctly).  The code
assumes the use of a 68000, and therefore doesn't set up the format word. 
This is instant death on a 68010 or 68020.

(I've posted this rather than emailed because people keep asking me about
MINIX on 68010 and 68020.  Perhaps I should do a FAQ ....)

Regards
Andy Michael



-- 
Andy Michael (eesrajm@cc.brunel.ac.uk)      " Emulation is the sincerest
85 Hawthorne Crescent                         form of pottery."
West Drayton
Middlesex                                    - William Frend De Morgan
UB7 9PA