I'll try:

 clrf c

 movf b,w      ;b = w
 btfsc a,0
  addwf c

 addwf b,w     ;w = b*2
 btfsc a,1
  addwf c

 movwf b       ;b = b*2
 addwf b,w     ;w = b*4
 btfsc a,2
  addwf c

 movwf b       ;b = b*4
 addwf b,w     ;w = b*8
 btfsc a,3
  addwf c

 .
 .
 .

 movwf b       ;b = b*64
 addwf b,w     ;w = b*128
 btfsc a,7
  addwf c

rgds,
Reggie
----- Original Message -----
From: Scott Dattalo <scott@DATTALO.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, November 14, 2001 3:43 AM
Subject: Challenge: 8X8 multiplication


> Suppose you have:
>
>  c = a * b
>
> and all three are bytes.
>
> Minimize execution time (on a mid-range core).
>
> Trashing a (or b) I have a routine that is 31 instructions/cycles long.
>
> Any takers?
>
> Scott
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
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>

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