On Wed, 15 Jan 2003, Wagner Lipnharski wrote:

> Kyrre Aalerud wrote:
> > Does anyone have any examples on fast 512 bit multiplication ?
> > I'm talking about 512bit x 512bit.
> >
> > Is there any PIC's that have a MULT operation easing this ?
> >
> >     KreAture
>
>
> I think there is no much to speed up the usual
>
> shift
> if carry bit then do a 64 bytes ADD
> decrement 512 loop counter
> do it again.

If you had a 256 bit multiplier, then it would only take 3 multiplications
to compute a 512-bit product. If you only a 128-bit, then it would take
3*3. If you had only a 64-bit multiplier, then it would take 3*3*3. If you
have an M-bit multiplier then it would take 3^(lg[512/M]) M-bit
multiplications (where lg[] is log base 2). On the 18F, that would be 3^6
= 729. Of course, there are also numerous additions as well.

Scott

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