Re: DD2 & 3

From: silverdr_at_wfmh.org.pl
Date: Wed, 19 Jun 2013 00:04:35 +0200
Message-Id: <91075D24-93B2-416F-A217-8E16C24EDD13@wfmh.org.pl>
On 2013-06-18, at 19:38, Jim Brain wrote:

>> For real reasons we would have to ask the creators themselves (I haven't found them on facebook yet ;-) but my best guess is that they wanted to be farsighted and less vulnerable to the whims of CBM than they were with the original design. Therefore they might have asked themselves the question "what if tomorrow Commodore takes more bits out or something?" "It's quite unlikely that they get rid of 6502 though so let's depend only on this one" - my guesses and speculations. Another thing is that they probably wanted the design to be applicable to many target devices without redesigning. No matter how laid out the controller's PCB is and whether there is a free port (be it VIA or CIA or whatever else) or not
> 
> I guess, but dubious.  CBM could have just went and stuffed something in the address map that contradicted the 6821 address space.

Sure. Still - unless they took out too much of the address space to fit 8KiB plus a few bytes - this kind of redesign (shifting positions) would probably be much easier than doing things from scratch.

> IN any event, it was an academic question.

Right. And I think that the more important was what Nicolas wrote: they could put the same PCB into each of the mentioned devices without h/w mods.

As for guesses, I think that the lack of the bit could have been the trigger for them to "have enough" of catching up with various controllers' boards.

-- 
SD!
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Received on 2013-06-18 23:00:08

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