MadeEasy Test Series: CO & Architecture - Pipelining

Question

please check the answer...

Comments

answer given

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there's one stall in I1 in ID stage, one stall in I3 for ID stage again and then two stall in I4 stage.

Answer 1

I0 : R2 <-- R0 + R1

I1 : R1 <-- R2 - R1

I2 : R0 <-- R2 - R0

I3 : R2 <-- R1 * R0

I4 : R3 <-- R1 + R0

I/C	1	2	3	4	5	6	7	8	9	10	11
I0	IF	ID	PO	MA	WB
I1		IF	ID	PO	MA	WB
I2			IF	ID	PO	MA	WB
I3				IF	ID	PO	PO	PO	MA	WB
I4					IF	X	X	ID	PO	MA	WB

in this instruction pipeline using operand forwarding so result are store in stage PO . Hence next instruction must used the result after PO stage.(where X represent no of stall)

Hence Total Stall = 2

Answer 2

ans is 2 and the given explation is correct

Comments

Bro see the daigram correctly I1 has only one ID but in diagram they have taken 2 ID..so total stall cycles will be 3 not 2..

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Can we do PO and MA in same cycle in case of operand forwarding insead of WB and PO in same cycle???

and why they are using 2 cycle for instruction fetch..please answer