fast division/multiplication

Press RESET immediately, All! I'm trying to make a screw driver for IS-DOS (and not only). And here it is necessary CHS addressing is recalculated in LBA and vice versa. If from CHS to LBA then it turns out two 16-bit multiplications, and if from LBA to CHS then one multiplication and two 16-bit division with remainder. And if you remember how long the spec divides 16-bit numbers then it becomes scary to think how it will slow down! One division leaves only a few thousand cycles, and not much less for multiplication. :-( You can optimize: ; HLDE=LBA, HL'=track DE'=sectors in a track LD B, 4 L1 EX DE, HL ADD HL, HL EX DE, HL ADC HL, HL DJNZ L1 LD B, 28 EXX LD HL, 0 LD DE, (HEADS*SECTORS) EXX L2 EX DE, HL ADD HL, HL EX DE, HL ADC HL, HL EXX CCF JR NC, L3 ADD HL, DE L3 ADC HL, HL EXX DJNZ L2 It turns out about 2 thousand cycles. :-( For ONE operation! :-( I haven’t tried to look at it with a disassembler yet - is it really like that for every screw driver? slows down? :-( ) * Originally in CODE.ZX * Crossposted in ZX.SPECTRUM