16 v. 32 bit

Jonathan P. Leech jon at cit-vax.arpa
Tue Dec 24 07:33:11 AEST 1985


>   The Motorola 68000 family of microprocessors ALL implement full 32-bit
> internal architecture. That means 32-bit registers, 32-bit data paths, and
> a 32-bit ALU. I recommend that you obtain FACTS next time instead of posting
> hearsay to the net. Try reading the Motorola MICROPROCESSOR COMPONENTS DATA
> MANUAL (or Hitachi's -- they're a second source) and then say "32 bits"
> until you're convinced.
>
>		  Dave Lewis	Loral Instrumentation	San Diego

    The 68000 has no 32 bit multiply or divide instructions. This does
not seem like a `full 32-bit internal architecture' to me. This  leads
to an interesting question: should 68000 C compilers have  sizeof(int)
== 16 bits or 32 bits? The common choice is  32,  I  suspect  so  that
poorly written VAX code would port without any work; but 16 bits seems
more natural given  the  limitations  of  32  bit  arithmetic  on  the
machine.

    Having a religious bias in favor of 68000s is fine - I  have  one,
too - but don't let it blind you to FACTS.

    -- Jon Leech (jon at cit-vax.arpa)
    __@/



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