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Newsgroups: bit.listserv.i-amiga
Date:         Fri, 16 Oct 1992 09:52:21 -0400
From:         "Daniel S. Riley" <dsr@LNS598.TN.CORNELL.EDU>
Subject:      Re: A4000 compatability

"The Large Guy with Buckwheat's Hair." <LANDAS88@SNYPOTVA.bitnet> writes:
>Really good question.  Is AmigaDos 3.0 100% compatible with 2.0.  Did Commodore
>finally get it right are their OSs gonna be backwords compatible 100% of the
>time now.

Well, they relinked the ROM image, so right off it can't be 100% compatible,
as some of the addresses have changed.  Worse, they *fixed* a *large* number
of bugs, so there's no hope of *100%* compatibility.  Just about all programs
that made a reasonable good-faith effort to follow the rules (which Commodore
has been publicizing since before the A1000 was released) work fine.  Programs
that break the rules may not.  3.0 is a little less forgiving in this respect
than 2.04, since they changed more, and had to remove some of the backwards-
compatibility-hacks-for-the-seriously-broken to make room in the ROMs for
neat new stuff.

As an example that things can be done right, MindWalker (one of the first
interesting Amiga games, written *before* 1.0 came out), still works under
3.0.  Yeah, it's nowhere near as flashy as the latest Psygnosis title, but
it was fun to play, multitasked cleanly, and has worked under *every* version
of the OS.  (ok, ok, it also has some minor sprite positioning problems with
overscan screens, but that's still pretty good...)

>I realize that it's actually the mainly the fault of many of the
>software developers, but if CBM had not allowed them to do so many "illegal"
>things.  Then 2.0 would run more 1.3 programs.

If you've got any (realistic) suggestions for how Commodore should prevent
people from writing bad programs, I'm sure they'd love to hear about it.
C= has been publishing rules for programming the Amiga since day -1, and
recently has been distributing tools like enforcer and mungwall which make
it *much* easier to catch some types of programming errors, but they can't
force people to follow the guidelines, or force them to use the developer
tools.

One step Commodore is taking to make bad programming practices harder--there
will not be a Hardware Reference Manual for the AA chips, with all the
register addresses and such.  Programmers that want to use AA features are
thus *strongly* encouraged to use the OS.

>What's going on the the
>AA chips I hear they are 100% compatible.  IS this autodetected or do I have to
>switch a mode like with my ROM switcher?????????

The AA chips come up in ECS compatibility mode, which they claim is 100%
compatible with the ECS chip set.  Once the OS comes up, it may set things
differently, but from then on any programs should be going through the OS
anyway.  So most games that run on a A3000 with a 68040 card should run on
the A4000 (but you never know quite how evil game programmers may get until
you actually try).

--
Dan Riley                          Internet:   dsr@lns598.tn.cornell.edu
Wilson Lab, Cornell University     HEPNET/SPAN: lns598::dsr (44630::dsr)
	 "Maybe, leastways is the best way of all" -Caterwaul
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU