Just be careful because the 68000 can't do misaligned word copies.
But yeah - with no instruction cache, you are usually dealing with
higher instruction bandwidth than data bandwidth! (I find myself
nowalways optimizing on the code side!)
So yes, definately, use move.l when you can -> for 2 bytes of
instructions you get 8 bytes of data bandwidth. :)
I'm a graphics developer, and it's really upside down for me now -> I
find myself saying, how can I draw more graphics as a way to save some
additional program logic and save instruction bandwidth? :)
Roger Chaplin wrote:
>
> Adam Wozniak <[EMAIL PROTECTED]> wrote:
>
> > Florent Pillet wrote:
> >
> > > I'm trying to determine the memory bus width on various Palm models, to be
> > > able to optimize large data transfers (i.e. using move.w or move.l
> > > instructions) but did not find any information about it.
> > >
> > > Anybody knows where I can get this information?
> >
> > Poking at the registers on my MC68328 based Palm VII tells me the bus
> > is 16 bits wide. Poking through the manual for the MC68EZ328 tells me
> > that you have two choices; 8-bit or 16-bit. I suspect wide moves are the
> > best you'll get.
>
> Seems to me that using the move.l instruction would be more efficient
> even though the bus is only 16 bits wide, especially using an address
> register indirect with increment addressing mode. If you have the chart
> that shows CPU/bus cycles for each instruction, see how many cycles
> each of the following code bits takes:
>
> 1$ move.l (a0)+,(a1)+
>
> 2$ move.w (a0)+,(a1)+
> move.w (a0)+,(a1)+
>
> I don't have the chart handy, but I would bet that the first takes
> fewer cycles than the second.
>
> --
> Roger Chaplin
> <[EMAIL PROTECTED]>
>
> --
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