A pipelined processor is executing the following instruction sequence:

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$1.$ LOAD R$2,0($R$1)$

$2.$ LOAD R$4,1($R$3)$

$3.$ SUB R$5,$ R$4,$ R$6$

$4.$ ADD R$8,$ R$5,$ R$7$

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The processor has two configurations:

With forwarding: Data is forwarded as soon as it's available

Without forwarding: Instructions dependent on results on results from previous instructions must stall until the result is written back

Assume:$$

Each instruction completes in $5$ cycles without stalls.

Data hazards only occur for read$-$after$-$write $($RAW$)$ dependencies.

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a$)$ With forwarding enabled, fill in the blanks below:

Instruction $1$ completes in cycle

Instruction $2$ completes in cycle

Instruction $3$ completes in cycle

Instruction $4$ completes in cycle

b$)$ Without forwarding, calculate the total number of stall cycles needed to handle data hazards

Instruction $1$ requires stall cycles$$

Instruction $2$ requires stall cycles

Instruction $3$ requires stall cycles

Instruction $4$ requires stall cycles

Total stall cycles $=$

c$)$ Total cycles: calculate the total number of cycles for the entire sequence with and without forwarding

With forwarding : cycles

Without forwarding: cycles