From: Dave Haynie (dhaynie@jersey.net)
Subject: Re: Why do you think...
 
View this article only
Newsgroups: comp.sys.amiga.misc
Date: 2004-03-16 06:18:51 PST

On Sun, 14 Mar 2004 09:59:36 GMT, ""Azrael" <afn04314ATafn.org>"
<"Azrael".<afn04314ATafn.org>@p0.f0.n0.z0.fidonet.org> wrote:

>In message <0043741b@elebbs.bbs>, Joona.I.Palaste@p0.f0.n0.z0.fidonet.org
>wrote: 
>> Backwards compatibility with the C64 for the Amiga is pretty much
>> impossible. T 
>I realize that it was impossible given the way in which it was designed. But
>it could have been designed in from the beginning and this was the point I
>was trying to make.

Ok... no, it couldn't have been. Period. End of story. C64
compatibility would have crippled in the Amiga in heinous ways, for
very little added value. 

There are times when it makes sense to try for backward compatibility,
and times when it doesn't. 

>Of course the Amiga wasn't designed by Commodore so that
>would never have been a consideration. It certainly would have been possible
>to do. I can run 8088 software on my P4

There is more in common between the original IBM PC and a modern PC
than between the C64 and the Amiga. And even at that, once things get
even a little complicated, what you claim isn't true. You probably
can't run most MS-DOS programs on a Windowx XP machine. Or CGA. Or
whatever that 1982-1985 PC used for sound. Stuff just isn't supported
anymore. But hey.. it'll all work in an emulator.

> and PS1 games on my PS2.

That was a design decision that probably did add complexity to the
PS2. But you're also talking about a totally different age. Sony's
making their own CPUs there, along with the graphics chips and all,
they're not using anything off-the-shelf in the PS2, other than the
Direct Rambus memories. Such things were not possible, at this level,
back in 1982-1983 (when the Amiga was started).

And even at that, it only works because of the way the PSX1 was done.
It's a game machine, and it only needs to talk to a small bit of I/O.
How would you get the unchanged C64 ROM loading programs from an Amiga
floppy or hard drive? With all the hacks, that sort of stuff never
worked very well on the C64 itself. You basically have to fool the C64
environment into thinking there's a 1541 (or something similar) there.
Especially when the C64 application launches a program on the 1541's
CPU :-). EMOULATORs. They do this perfectly, without complicating the
new thing.

Read the rest of this message...thing.

This isn't that unusual. While you guys never saw this done, of
course, C= was tossing any backward compatibility with the Amiga
chipset with the "Hombre" project (the successor to AAA). And AAA
itself -- the 64-bit Amiga chipset. That took extra years simply
because it was trying to stay compatible with the original chipset.
That compatibility was inherently broken in 64-bit systems anyway, the
whole thing got expensive (four large chips in a 32-bit system, six
large chips in a 64-bit system, VRAM, etc). It would have been far
better to toss out bit-level compatibility for AAA. Maybe it would
have been finished before C= tanked. 

The issue, of course, is the growth of operating systems. In the
modern world, you can throw out pretty much anything but the CPU
itself (even the CPU if you're clever, like the Transmeta CPUs), and
still run the old applications. That's precisely because they don't
bang any registers, etc. They always talk to device drivers. This was
almost universal in the Amiga; graphics was very nice, but far too
close to the metal. It made the Amigas fast in the early days, but it
was a boat anchor after about 1988 or so. 

>It's not even close to an impossible task.

In mathematical terms, <impossible> - <epsilon> = <impractical>

In engineering terms, we toss out the insignificant issues, and thus,
<impractical> == <impossible>. If there's no proper way to do it, it
can't be considered, even if you could actually do it, given enough
effort, cost, and/or compromise. 
Dave Haynie       | Chief Toady, Frog Pond Media Consulting
dhaynie@jersey.net| Take Back Freedom! Bush no more in 2004!
"Deathbed Vigil" now on DVD! See http://www.frogpondmedia.com