21 Nov
2009
21 Nov
'09
7:19 p.m.
What about the story of the first revision, the 6501,
which was pin
compatible with the Motorola 6800(being that they were ex-MOT people)
but offered more addressing modes. From what I read, this was their
intention in order to gain a foothold in the market Although it wasn't
software compatible from what I understand--so I'm not sure how they
AFAIK the 6501 was software compatible with the 6502, which makes it
incompatile with the 6800.
expected to gain any advantage. Then Motorola sued
them in court and
won, and this resulted in them making the 6502.
Of course the signals remained logically the same, just on different
pins. And the 6502 could use all the peripehral chips for the 6800 very
easily.
I have seen at least one PCB (I think the one I remember came from
Tangerine) which has overlapping 40-pin DIL positions for either a 6502
0r a 6800. Oviously you needed diferent monitor ROMs and software, but
the hardwre was essnetially the same. I heard a rumour the Apple 1 had
that feature too, but I have never handled one...
-tony