Re: The Apple ][ was cool!

[dempson@actrix.gen.nz (David Empson)]

william strutts <wrstrutts1@nospam.home.com> wrote:

> "David Empson" <dempson@actrix.gen.nz> wrote in message
> 1ewrul3.1lppa9z118k0snN%dempson@actrix.gen.nz">news:1ewrul3.1lppa9z118k0snN%dempson@actrix.gen.nz...
> <snip>
> > I'd dispute that.  The 6809 has an 8-bit accumulator and ALU, and uses
> > an internal 8-bit data path.  It combines 8-bit accumulators to form a
> > 16 bit pair, which allow a smaller set of 16-bit operations.  It also
> > has the address space typical of an 8-bit processor (64KB).  Even
> > Motorola call it an 8-bit micro in the data sheet.
> >
> > Sounds like an 8-bit micro to me.
> 
> Well, I would suppose if we refer to the ALU as the primary
> factor. I would have to agree.  I was referring more to the
> fact that the processor had built-in 16-bit operations via
> register combining.  It was marketed back in the 80's as
> an 8/16 bit processor.  The later 68HC11 would further
> extend the 16 bit features of the 6809 and move it into
> the realm of 1 meg address space and more 16-bit
> operations making it a 16-bit computer.

The 68HC11 is not derived from the 6809.  It is actually an extended
6801.  It is also strictly an 8-bit processor with 64K address space and
some 16-bit capabilities.  (Some models may have bank switching features
to extend the address space.)  You might be thinking of the 68HC16,
which is a 16-bit processor derived from the 68HC11.

The 6800 is the daddy of the whole family, with 8-bit A and B
accumulators and a 16-bit X index register.  It is a plain
"microprocessor", with no embedded peripherals.  The 6802 and 6808 were
simple variants with different hardware clock interfaces.

The 6801 and 6803 are code compatible with the 6800, but adds extra
features: a D accumulator which combines A and B, and several extra
instructions.  They are also classed as "microcontrollers", with
embedded peripherals (RAM, digital I/O, and also ROM in the case of the
6801).

The 68HC11 family adds more features to the 6801: a Y index register,
even more instructions, and a much wider variety of peripherals.  The
instruction set is a superset of the 6801.

The 6809 is a side branch from the 6801, which is a significant
functional improvement but losing machine code compatibility.  The 68000
is the logical successor of the 6809.

The 6805 and 68HC08 are even simpler microcontrollers, which are also
incompatible with the 6800 at the machine code level, but which have a
similar architecture.  (I think the 6805 has an 8-bit index register,
making it more like the 6502.)