base:fastest_multiplication
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base:fastest_multiplication [2021-02-23 04:49] – fix typo in example usage strobe | base:fastest_multiplication [2023-08-21 02:45] – repose | ||
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Mine: 196 zp variation: 192 \\ | Mine: 196 zp variation: 192 \\ | ||
Times above need to add 12 for jsr/rts \\ | Times above need to add 12 for jsr/rts \\ | ||
+ | Note: updated 2023; corrected typos and timings \\ | ||
< | < | ||
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;do_add: 30 bytes in zp, if used | ;do_add: 30 bytes in zp, if used | ||
;time: 196 cycles, option for 192 if you use 30 more zp bytes for do_add | ;time: 196 cycles, option for 192 if you use 30 more zp bytes for do_add | ||
- | ; | + | ; |
;How to use: | ;How to use: | ||
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z0=$80; | z0=$80; | ||
z1=$81 | z1=$81 | ||
- | ;z2=$82 returned in X reg | + | z2=$82 |
- | ;z3=$83 returned in Y reg | + | z3=$83 |
;Example showing use | ;Example showing use | ||
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jsr makesqrtables | jsr makesqrtables | ||
jsr umult16 | jsr umult16 | ||
+ | stx z2 | ||
+ | sty z3 | ||
;result should be $fffe0001, e.g. as viewed with a typical m 0080 monitor command: | ;result should be $fffe0001, e.g. as viewed with a typical m 0080 monitor command: | ||
;0080 01 00 fe ff | ;0080 01 00 fe ff | ||
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sta p_invsqr_hi; | sta p_invsqr_hi; | ||
- | ldy y0 | ||
sec | sec | ||
+ | ldy y0 | ||
lda (p_sqr_lo), | lda (p_sqr_lo), | ||
- | sbc (p_invsqr_lo), | + | sbc (p_invsqr_lo), |
sta z0;x0*y0l | sta z0;x0*y0l | ||
lda (p_sqr_hi), | lda (p_sqr_hi), | ||
sbc (p_invsqr_hi), | sbc (p_invsqr_hi), | ||
- | sta c1a+1; | + | sta c1a+1; |
;c1a means column 1, row a (partial product to be added later) | ;c1a means column 1, row a (partial product to be added later) | ||
ldy y1 | ldy y1 | ||
- | ;sec ;notice that the high byte of sub above is always | + | ;sec ;notice that the high byte of subtraction |
lda (p_sqr_lo), | lda (p_sqr_lo), | ||
sbc (p_invsqr_lo), | sbc (p_invsqr_lo), | ||
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lda (p_sqr_hi), | lda (p_sqr_hi), | ||
sbc (p_invsqr_hi), | sbc (p_invsqr_hi), | ||
- | sta c2a+1; | + | sta c2a+1; |
;set multiplier as x1 | ;set multiplier as x1 | ||
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lda (p_sqr_hi), | lda (p_sqr_hi), | ||
sbc (p_invsqr_hi), | sbc (p_invsqr_hi), | ||
- | sta c2b+1; | + | sta c2b+1; |
ldy y1 | ldy y1 | ||
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lda (p_sqr_hi), | lda (p_sqr_hi), | ||
sbc (p_invsqr_hi), | sbc (p_invsqr_hi), | ||
- | tay; | + | tay; |
- | ;17+33+31+17+31+30=159 cycles for main multiply part | + | ;17+34+33+17+33+31=164.97 |
;jmp do_adds; can put do_adds in zp for a slight speed increase | ;jmp do_adds; can put do_adds in zp for a slight speed increase |
base/fastest_multiplication.txt · Last modified: 2024-02-13 08:24 by repose