At 11:58 PM 1/1/01 +0000, Tom Hughes wrote:
>In message <[EMAIL PROTECTED]>
> Dan Sugalski <[EMAIL PROTECTED]> wrote:
>
> > At 09:48 PM 12/30/00 +0000, Nick Ing-Simmons wrote:
> >
> > >ARM7/ARM9 are both 32-bit
> > >MIPS has both 32-bit and 64-bit variants.
> >
> > That's good. Though do either of them have 16-bit data busses?
>
>If you ignore thumb mode all ARM chips are 32 bit as far as the data
>bus and registers go, at least at the CPU core interface. You could
>of course hook up a 16 bit bus to the core and force the high bits to
>always be zero or similar. Offhand I can't remember if thumb mode
>uses 16 bit data as well as 16 bit instructions.
I was thinking of chips like the 68008, which had a 16-bit data bus. While
the native word size was 32 bits, fetching one took two trips out to
memory. Done automagically for you by the chip's circuitry so you didn't
have to worry, but 16-bit integers were markedly faster to use than 32-bit
ones.
Nobody may do that any more, but I think extra pins off a chip still cost
something, so they may still do it.
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
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