Re: Motherboard chip descriptions?

[et472@FreeNet.Carleton.CA (Michael Black)]

"Ernest" (leucoplast@seanet.NOSPAMS.com) writes:
> Does anyone know of a book or website that describes what each of the
> different ICs (74LS* chips) on the Apple II and clone motherboards do? I'm
> going to be starting a "compare and contrast" project between the Apple II+
> and my different clone motherboards, which often have some interesting
> differences. If I can figure out what each of the different chips are for,
> then I might be able to better understand why chips were added or removed on
> different boards. That's my hope anyway.
> 
As others have pointed out, it's really easy to find information on
common ICs on the internet, and that's what makes up the Apple II.

But since most of the ICs in an Apple II are at most medium scale integration,
I'm not sure they will tell you much about a clone board.  That 7400 over
here could be the same as that 7400 over there, or it could be combined
in a different fashion to do something else.  Other than the 6502, and
I suppose the 558 quad timer for the joysticks, there isn't much that
you can be absolutely sure of by looking at the IC number.  More integrated
ICs can be used for one or only a handful of functions, so you can immediately
tell what it's doing.  For instance if a Z80 appears on the board, then the
clone has got to have built in CPM capabilities (unless there was a clone
that had some really weird function thrown in).  If you find an IC that is
an analog to digital converter, then you know the clone has some intriguing
extra inputs.

Surely your most important source of information for this sort of thing
is the original Apple II manual.  It has a large foldout schematic at the
back, and earlier in the book it has a breakdown by section of the circuit.
Understand that, and you'll have a better understanding of what might be
extra on a clone.  It's the function that counts, not the common IC
numbers.

  Micahel