Faster multiply?

[boriel]

Ok, this is an interesting issue. I tried a supposed faster 8-bit multiplication taken from internet, but it was failing, so I implemented another by myself.

Let me repost your code here, for better clarification:

Code:

LD HL,0 LD DE, (NUM2) LD A, (NUM1) LOOP: RR A ; (Divide A by 2 - copying the 1's column bit into the carry flag.) JR NC, JP1; (Jump over the add if we have to) ADD HL,DE JP1: RET Z ; (Leave when we finish - A has gone to zero) SLA E RL D ; Multiply DE*2 JR LOOP

I will later study this case.