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The importance of having a good branch predictor depends on how often conditional branches are executed

Computer Science

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The importance of having a good branch predictor depends on how often conditional branches are executed. Together with branch predictor accuracy, this will determine how much time is spent stalling due to mispredicted branches. In this exercise, assume that the breakdown of dynamic instructions into various instruction categories is as follows:

 

R-Type BEQ JMP LW SW

40% 25% 5% 25% 5%

 

Also, assume the following branch predictor accuracies:

 

Always - Taken Always-Not-Taken 2-Bit

40% 60% 85%

 

, Some branch instructions are much more predictable than others. If we know that 80% of all executed branch instructions are easy-to-predict loop-back branches that are always predicted correctly, what is the accuracy of the 2-bit predictor on the remaining 20% of the branch instructions?