There was some discussion at MARCH yesterday when we were talking about the
6501, and subsequently the 6502 and 6510. The subject was about what the
difference was between the 6502 and the 6510. I couldn’t remember exactly
the difference, so I did some research and just wanted to share for those
that don’t know already.
This article: http://urql.com/xbue
basically says that the first two bytes
of 6510 are different, which allow bank switching of memory.
This site: http://urql.com/esmt
seems to say that there are additional
undocumented "illegal" opcodes added to the 6510 that were not available in
adds: "The primary
change from the 6502 was the addition of an 8-bit general purpose I/O port
(only six I/O pins were available in the most common version of the 6510).
In addition, the address bus could be made tristate. In both the C64 and
SX-64 the extra pins of the processor were used to control the computer's
memory map by bank switching, and in the C64 also for controlling three of
the four signal lines of the Datassette tape recorder (the electric motor
control, key-press sensing and write data lines; the read data line went to
another I/O chip). "