Re: Amiga, Mac, Atari

["Pete" <my.name@wintermute.org.uk>]

Hi,

  >> My gut feeling is that the 6507 was a cheaper chip (well it
  >>SHOULD have been) but does anyone know for sure?

  > It wouldn't matter because all it would have done was change
  >the price maybe a dollar.

OK, I'll admit I was being a tad vage....the 6507 *SHOULD* have been a
cheaper device than the full 6502 since it was being aimed at the embedded
controller/small system market.

That said, since AFAIK both processors used exactly the same die just how
much cheaper was the 6507 in quantity?

However, even if it was only a dollar cheaper that would make a hell of a
difference when you're buying them in quantity....companies like Atari would
be buying tens of thousands at a time!


  > Hint: You don't have have the traces tied to all the lines....

AFAIK Internally the 6507 was identical to the 6502, IE they used the same
die, just that they didn't bring out the upper four address lines.

This would effectively give you a 64K address space made up of 16
reflections of the lower 4K. Which, as you say, is the same as leaving the
upper four address lines of the 6502 unconnected.

  >....The rest of the design would have still been the same. It you
  >only wanted 4 KB, all you do is tie traces (to and from the memory)
  >to only 12 pins. Only have 12 traces.

Ah, but you're missing the other main feature of the 6507. The 6507 came in
a smaller (28 pin??) package, rather then the more standard 40 pin package
that the 6502 came in.


  TTFN - Pete.