Re: The apple 2, the PC, and the clones

[mjmahon@aol.com (Michael J. Mahon)]

David Wilson wrote:

>"Paul Grammens" <grammens@svn.net> writes:
>>Yes, I also found this very interesting and educational. I didn't know the
>>details of why IBM clones were legal but Apple clones generally weren't. I
>>thought IBM facilitated the cloning.
>
>The problem with cloning the Apple // firmware is that there are no INT
>vectors - all the monitor routines are at fixed addresses. This makes it
>difficult to replicate without using the same instructions. Had the monitor
>been written with a jump table at the front it would have taken up more space
>and been more easily cloned.

And there wouldn't be so many "PEEKs, POKEs, and CALLs charts".  ;-)

Although Apple was quite clear about the monitor entry points they
"supported" across revisions, software authors felt pretty free to use
any monitor routine they could find in the listing.  Perhaps including
a full monitor listing was too much of a double message...

-michael

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