Orthogonality and contrivedness

[Tim Shoppa]

Chuck writes:
> I work with both PICs and AVRs (my current project uses an 
> ATMega128), but both instruction sets seem to me to be more than a 
> bit contrived.  The AVR less so than the PIC, but still on the "odd" 
> side of the ledger.

Try programming an 1802 for a while. You'll know you're really into
it when it seems "contrived" that all those other processors can
only use a single of their registers as a program counter :-).
Twisting my mind to switch to 1802 mode and back is a interesting
experience.

The smaller PIC's make perfect sense once you realize they're
Harvard architecture. Bigger PIC's, I never really grokked.

> I'm not a 430 evangelist (and suspect that it will never enjoy the 
> popularity of the PIC or AVR, which is a shame). I'll work with any 
> instruction set, but I know what I'd prefer to use.
>
> It's curious that the MSP430's instruction set is close to the GI 
> CP1600, where the PIC is descended from the very different 1650.

To me it's perfectly obvious that the MSP430 is PDP-11 like, and
in some ways even more orthogonal than the -11. The CP1600 was
substantially less orthogonal, more Nova-like with some
of the registers obviously intended for index use.

Tim.