Re: What Is The Difference Between 68000 Chip And 80x86 Chip?

[Roy Miller <millers@inetnebr.com>]

David Empson wrote:

> rWill Strutts <wrstrutts1@nospam.home.com> wrote:
>
> > "Paul Schlyter" <pausch@saaf.se> wrote in message
> > news:9uj3m0$6m9$1@merope.saaf.se...
> > > In article <1f3x0ks.7ta1x6r3r2u8N%dempson@actrix.gen.nz>,
> > > David Empson <dempson@actrix.gen.nz> wrote:
> > >
> > > > Here are the main differences which occur to me:
> > > >
> > > > - The 6800 has two 8 bit accumulators (A and B) which can be used almost
> > > > interchangably, while the 6502 only has one (A).
> > > >
> > > > - The 6800 has a single 16 bit index register (X), and the only indexing
> > > > method supported is "constant 8 bit unsigned offset from X", which is
> > > > implemented pretty uniformly on the core instructions; the 6502 has two
> > > > 8 bit index registers (X and Y), with a mixture of addressing modes
> > > > (zero page or absolute indexed, indirect with pre-indexing or
> > > > post-indexing depending on the register) with the full set only being
> > > > available on a limited group of instructions.
> > >
> > > I've been programming both the 6800 and the 6502 in assembly, and I
> > > found the single 16-bit index register of the 6800 more awkward than
> > > the dual 8-bit index registers of the 6502: the latter were clearly
> > > superior when you needed to move a block of data, less than 256 bytes
> > > large, from one address to another address more than 256 bytes away,
> > > which wasn't an uncommon situation.
> > >
> > The 6809 variant has a Y register too along with a multiply and
> > divide instruction.
>
> We were talking about the 6800.
>
> The 6809 is a different kettle of fish.  It is based on the 6800, but
> has a much more flexible architecture and instruction set.  It retains
> assembly language source compatibility (for the most part) but cannot
> execute 6800 machine code directly due to different opcodes being used.
>
> If we want to get into talking about 6800 derivatives, I could bore
> everyone silly with details about a few of them.

You didn't bore me with the data on the 6801... but then, it helped me understand
what my ADAM is doing while it's printing or loading data, or both at the same
time.

Thanks to the ADAMNet, and the 6801, printing, and loading data, and even editing
on the screen can all happen at the same time - not bad with a Z-80....

Roy