Re: A85: Fast 8 bit multiply routine
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Re: A85: Fast 8 bit multiply routine
Michael Pearce wrote:
>
> Does any one have a good (fast) routine to multiply 2, 8 bit numbers
> together?
>
> -mike pearceDepends on your situation. Here are some common solutions:
ld b,1st number
ld e,2nd number
ld d,0
ld hl,0
Loop:
add hl,de
djnz Loop
The result is a 16 bit number in hl. By the way, if b=0 then hl=256*e, if e=0
then hl=0. If the result will always be <256 then this should be faster
ld b,1st number
ld e,2nd number
xor a ;ld a,0
Loop:
add a,e
djnz Loop
Same traps. If you want to multiply by 2^x, do this:
ld b,x
ld l,first number
ld h,0
Loop:
add hl,hl
djnz Loop
Those routines may not be the fastest but should give you some ideas.
--
Terry Peng
email- tpeng@geocities.com
web- http://www.geocities.com/SiliconValley/Bay/5104/index.html
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