[Coco] Kicking the Z-80 butts...

[Hugo Dufort]

I've always found this "8-bit vs 16-bit classification" debate quite 
strange.
Most processors of the early late 1970s to early 1980s era had a mostly 
8-bit structure. Their working registers and most operations were mostly 
8-bit.
Sure you have a D register on the 6809, but most operations (especially 
bitwise operations) are strictly 8-bit (A, B). The joint A:B=D register 
is necessary to use the multiplication results, for instance, or to 
manipulate memory addresses.
Having a joint 2x 8-bit register (A:B=D) and 3x 16-bit address registers 
don't qualify as "16-bit computing" in my opinion.
You can't perform much accumulator-like operations on X,Y and U. Except 
for LD, ST and LEA.

And if you look at true 16-bit processors such as the M68k, they all had 
a few 32-bit operations, as well as 32-bit "joint" registers, but that 
don't make them "32-bit processors".

It is the same for all generations of processors.

Hugo

Le 2015-04-28 15:49, Dennis Bathory-Kitsz a écrit :
> On Tue, April 28, 2015 9:24 am, CoCo Demus wrote:
>> Who needs a Z-80 anyway ???
> Ha! Okay, can I bit?
>
> It's kind of an unfair comparison as the 6809 is really a 16-bit machine on an
> 8-bit bus. Take out those 16-bit structures and you're pretty much left with a
> 6502 -- the most elegant processor of all time, I think.
>
> My first published article was in "Byte" in 1979: "Relative Subroutines for
> the Z-80", emulating the 6502's behavior.
>
> Now give a Z-80 a 16-bit internal structure...
>
> No, don't answer me! :) :)
>
> Dennis
>
>
>


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