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

["Will Strutts" <wrstrutts1@nospam.home.com>]

"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.
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William R. Strutts - wrstrutts1@nospam.home.com - Whatever!

C'est moi!  http://www.facelink.com/wrstrutts

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