Question $9$

On typical embedded CPUs like PICORV why is not$-$taken branch prediction often implement instead of taken?

A: not$-$taken branches have higher prediction rate

B: not$-$taken misprediction incurs less misprediction stalls.

C$.$ not$-$taken is less expensive to implement.

not$-$taken doesn't requires the BTB to work.

B$,$D

$A,B,C,D$

C$,$D

B$.$C$.$D

Question $10$

Assume a $2-$bit branch predictor with a $4-$entry history table initialized to "Not taken $($value $0)."$

Consider the following sequence of branch outcomes $($T for taken, NT for not taken$)$ for branches accessed in the order given by PC value $080000000,080000001,080000002,$ and $080000003$ respectively: $,NT,T,T.$

Calculate the accuracy of the two$-$level branch predictor for the given sequence of branch outcomes.

Question $11$

Assume a two$-$level branch predictor uses a $2-$bit counter $4-$entry history table initialized to "Weakly Taken $($value $2)."$

Consider the following sequence of branch outcomes $($T for taken, NT for not taken$)$ for branches accessed in the order given by PC value $080000000,080000001,080000002,$ and $080000003$ respectively: T$,$ NT$,$ T$,$ T$.$

Assume the BHR is cleared to zero at initialization.

Calculate the accuracy of the two$-$level branch predictor for the given sequence of branch outcomes.

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