【正文】 h Preexecution mit HardwareBased Speculation Advantages of speculation ? Load and store hazard – a store updates memory only when it reaches the head of the ROB – WAW and WAR hazards through memory are eliminated with speculation ? actual updating of memory occurs in order – RAW hazards through memory are maintained by ? not allowing a load to initiate the second step of its execution ? Check if any store has an Destination field that matches the value of the load store r1, 100(r2) load r3, 100(r2) 作業(yè) 6 ? （英文版第五版） 作業(yè) 7 ? （英文版第五版） 。 what is waiting for it? 2022/8/17 32 Tomasulo Example Cycle 16 I ns tr uc ti on s tat us : E xec W r i t eIns t ruc t i on j k Is s u e Co m p R es u l t Bu s y A d d res sLD F6 34+ R2 1 3 4 L oa d1 NoLD F2 45+ R3 2 4 5 L oa d2 NoM U L T D F0 F2 F4 3 15 16 L oa d3 NoS U BD F8 F6 F2 4 7 8D IV D F 10 F0 F6 5ADDD F6 F8 F2 6 10 11R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam e Busy Op Vj Vk Qj QkA dd1 NoA dd2 NoA dd3 NoM ul t 1 No40 M ul t 2 Y e s D IV D M *F 4 M (A 1)R e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 3016 FU M *F 4 M (A 2) (M M + M )(M M ) M ul t 2? Just waiting for Mult2 (DIVD) to plete 2022/8/17 33 Faster than light putation (skip a couple of cycles) 2022/8/17 34 Tomasulo Example Cycle 55 I ns tr uc ti on s tat us : E xec W r i t eIns t ruc t i on j k Is s u e Co m p R es u l t Bu s y A d d res sLD F6 34+ R2 1 3 4 L oa d1 NoLD F2 45+ R3 2 4 5 L oa d2 NoM U L T D F0 F2 F4 3 15 16 L oa d3 NoS U BD F8 F6 F2 4 7 8D IV D F 10 F0 F6 5ADDD F6 F8 F2 6 10 11R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam e Busy Op Vj Vk Qj QkA dd1 NoA dd2 NoA dd3 NoM ul t 1 No1 M ul t 2 Y e s D IV D M *F 4 M (A 1)R e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 3055 FU M *F 4 M (A 2) (M M + M )(M M ) M ul t 22022/8/17 35 Tomasulo Example Cycle 56 I ns tr uc ti on s tat us : E xec W r i t eIns t ruc t i on j k Is s u e Co m p R es u l t Bu s y A d d res sLD F6 34+ R2 1 3 4 L oa d1 NoLD F2 45+ R3 2 4 5 L oa d2 NoM U L T D F0 F2 F4 3 15 16 L oa d3 NoS U BD F8 F6 F2 4 7 8D IV D F 10 F0 F6 5 56ADDD F6 F8 F2 6 10 11R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam e Busy Op Vj Vk Qj QkA dd1 NoA dd2 NoA dd3 NoM ul t 1 No0 M ul t 2 Y e s D IV D M *F 4 M (A 1)R e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 3056 FU M *F 4 M (A 2) (M M + M )(M M ) M ul t 2? Mult2 (DIVD) is pleting。 what is waiting for it? 2022/8/17 24 Tomasulo Example Cycle 8 I ns tr uc ti on s tat us : E xec W r i t eIns t ruc t i on j k Is s u e Co m p R es u l t Bu s y A d d res sLD F6 34+ R2 1 3 4 L oa d1 NoLD F2 45+ R3 2 4 5 L oa d2 NoM U L T D F0 F2 F4 3 L oa d3 NoS U BD F8 F6 F2 4 7 8D IV D F 10 F0 F6 5ADDD F6 F8 F2 6R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam e Busy Op Vj Vk Qj QkA dd1 No2 A dd2 Y e s ADDD (M M ) M (A 2)A dd3 No7 M ul t 1 Y e s M U L T D M (A 2) R(F 4)M ul t 2 Y e s D IV D M (A 1) M ul t 1R e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 308 FU M ul t 1 M (A 2) A dd2 (M M ) M ul t 22022/8/17 25 Tomasulo Example Cycle 9 I ns tr uc ti on s tat us : E xec W r i t eIns t ruc t i on j k Is s u e Co m p R es u l t Bu s y A d d res sLD F6 34+ R2 1 3 4 L oa d1 NoLD F2 45+ R3 2 4 5 L oa d2 NoM U L T D F0 F2 F4 3 L oa d3 NoS U BD F8 F6 F2 4 7 8D IV D F 10 F0 F6 5ADDD F6 F8 F2 6R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam e Busy Op Vj Vk Qj QkA dd1 No1 A dd2 Y e s ADDD (M M ) M (A 2)A dd3 No6 M ul t 1 Y e s M U L T D M (A 2) R(F 4)M ul t 2 Y e s D IV D M (A 1) M ul t 1R e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 309 FU M ul t 1 M (A 2) A dd2 (M M ) M ul t 22022/8/17 26 Tomasulo Example Cycle 10 I ns tr uc ti on s tat us : E xec W r i t eIns t ruc t i on j k Is s u e Co m p R es u l t Bu s y A d d res sLD F6 34+ R2 1 3 4 L oa d1 NoLD F2 45+ R3 2 4 5 L oa d2 NoM U L T D F0 F2 F4 3 L oa d3 NoS U BD F8 F6 F2 4 7 8D IV D F 10 F0 F6 5ADDD F6 F8 F2 6 10R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam e Busy Op Vj Vk Qj QkA dd1 No0 A dd2 Y e s ADDD (M M ) M (A 2)A dd3 No5 M ul t 1 Y e s M U L T D M (A 2) R(F 4)M ul t 2 Y e s D IV D M (A 1) M ul t 1R e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 3010 FU M ul t 1 M (A 2) A dd2 (M M ) M ul t 2? Add2 (ADDD) pleting。 what is waiting for Load1? 2022/8/17 20 Tomasulo Example Cycle 4 I ns tr uc ti on s tat us : E xec W r i t eIns t ruc t i on j k Is s u e Co m p R es u l t Bu s y A d d res sLD F6 34+ R2 1 3 4 L oa d1 NoLD F2 45+ R3 2 4 L oa d2 Y e s 45+ R3M U L T D F0 F2 F4 3 L oa d3 NoS U BD F8 F6 F2 4D IV D F 10 F0 F6ADDD F6 F8 F2R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam