• Re: The Mega II, was Re: How does the Apple IIGS emulate a IIe?

    From Yeechang Lee@ylee@columbia.edu to comp.sys.apple2 on Tue Feb 13 12:11:51 2024
    From Newsgroup: comp.sys.apple2

    D Finnigan wrote:
    He further said: "The Mega II "Apple II on a chip" is the Ball and Chain of the GS -- it was originally designed for a low cost //e but wasn't cheap enough to make the //e any cheaper. (to Apple, apparently. Certainly not to us.)

    When they get rid of it and implement the logic where it belongs (i.e. all over the machine and integrated into the custom chips that handle each part of the system already) it will blow away the performance limitations of the current design and cost a hell of a lot less.

    Apple made the same mistake that Commodore did a year earlier: Implement backward compatibility in a discrete "system on a chip" (such as Mega II) that advances in VLSI made possible. While providing 100% compatibility, by walling off the "old" and "new" modes from each other, software developers had to choose one to support and of course chose the mode with the far larger installed base.

    What both companies should have done is implement the new features within the existing software and hardware interfaces, as Apple had done with double hi-res, 80-column text, and lowercase. This would have decreased the level of backward compatibility, but developers would have released updated versions of existing software (just as software incompatible with IIe and IIc quickly got updated), and the IIgs would have benefited in the long run. Similarly, Commodore should have designed the 128 as a 64 with more memory, 80-column support, and a better BASIC. Again, backward compatibility would have been impacted, but over the long run there would have been more incentive for developers to release software that supports the 128's enhancements, and to update existing incompatible software.

    One can argue—probably accurately—that Commodore would not have done this given its record of (lack of) backward compatibility, and that the 128 having a 64-on-a-chip is the most to be hoped for. But Apple did have both the history of incremental improvements and commitment to backward compatibility, so there is less excuse there. On the other hand, it's understandable how seductive the promise of being able to provide 100% backward compatibility with a single chip was.
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