【正文】 (WB) Write on Common Data Bus to all awaiting units。 mark reservation station available 2022/8/17 15 Three Stages of Tomasulo Algorithm ? Normal data bus: data + destination (―go to‖ bus) ? Common data bus: data + source (―e from‖ bus) –64 bits of data + 4 bits of Functional Unit source address –Write if matches expected Functional Unit (produces result) –Does the broadcast ? Example speed: –3 clocks for Flopt. +,。 –10 clocks for Flopt. * 。 –40 clocks for Flopt. / 2022/8/17 16 Tomasulo Example 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 L oa d1 NoLD F2 45+ R3 L oa d2 NoM U L T D F0 F2 F4 L oa d3 NoS U BD F8 F6 F2D 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 e Busy Op Vj Vk Qj QkA dd1 NoA dd2 NoA dd3 NoM ul t 1 NoM ul t 2 NoR e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 300 FUClock cycle counter FU count down Instruction stream 3 Load/Buffers 3 FP Adder . 2 FP Mult . 2022/8/17 17 Tomasulo Example Cycle 1 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 L oa d1 Y e s 34+ R2LD F2 45+ R3 L oa d2 NoM U L T D F0 F2 F4 L oa d3 NoS U BD F8 F6 F2D 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 e Busy Op Vj Vk Qj QkA dd1 NoA dd2 NoA dd3 NoM ul t 1 NoM ul t 2 NoR e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 301 FU L oa d12022/8/17 18 Tomasulo Example Cycle 2 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 L oa d1 Y e s 34+ R2LD F2 45+ R3 2 L oa d2 Y e s 45+ R3M U L T D F0 F2 F4 L oa d3 NoS U BD F8 F6 F2D 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 e Busy Op Vj Vk Qj QkA dd1 NoA dd2 NoA dd3 NoM ul t 1 NoM ul t 2 NoR e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 302 FU L oa d2 L oa d1Note: Can have multiple loads outstanding 2022/8/17 19 Tomasulo Example Cycle 3 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 L oa d1 Y e s 34+ R2LD F2 45+ R3 2 L oa d2 Y e s 45+ R3M U L T D F0 F2 F4 3 L oa d3 NoS U BD F8 F6 F2D 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 e Busy Op Vj Vk Qj QkA dd1 NoA dd2 NoA dd3 NoM ul t 1 Y e s M U L T D R(F 4) L oa d2M ul t 2 NoR e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 303 FU M ul t 1 L oa d2 L oa d1? Note: registers names are removed (“renamed”) in Reservation Stations。 MULT issued ? Load1 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 e Busy Op Vj Vk Qj QkA dd1 Y e s S U BD M (A 1) L oa d2A dd2 NoA dd3 NoM ul t 1 Y e s M U L T D R(F 4) L oa d2M ul t 2 NoR e gis te r r e s ult s tat us :C loc k F0 F2 F4 F6 F8 F 10 F 12 ... F 304 FU M ul t 1 L oa d2 M (A 1) A dd1? Load2 pleting。 what is waiting for Load2? 2022/8/17 21 Tomasulo Example Cycle 5 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 4D IV D F 10 F0 F6 5ADDD F6 F8 F2R e s e r v ati on Stat ions : S1 S2 RS RST i m e Nam e Busy Op Vj Vk Qj Qk2 A dd1 Y e s S U BD M (A 1) M (A 2)A dd2 NoA dd3 No10 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 305 FU M ul t 1 M (A 2) M (A 1) A dd1 M ul t 2? Timer starts down for Add1, Mult1 2022/8/17 22 Tomasulo Example Cycle 6 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 4D 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 Qk1 A dd1 Y e s S U BD M (A 1) M (A 2)A dd2 Y e s ADDD M (A 2) A dd1A dd3 No9 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 306 FU M ul t 1 M (A 2) A dd2 A dd1 M ul t 2? Issue ADDD here despite name dependency on F6?