Consider a local branch predictor that 10 bits of branch PC is used for indexing into its level-1 that has 14-bit history entries. These 14 bits from level-1 are XOR-ed with 14 bits of branch PC to generate the index into level-2 that has 2-bit saturating counters. What is the total size of this branch predictor

Question

Computers & Technology

Jaelyn Glover

8 September, 13:57

Consider a local branch predictor that 10 bits of branch PC is used for indexing into its level-1 that has 14-bit history entries. These 14 bits from level-1 are XOR-ed with 14 bits of branch PC to generate the index into level-2 that has 2-bit saturating counters. What is the total size of this branch predictor

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Dallas Underwood · Answer 1

16384 entries

Explanation:

The total size of the branch predictor (which is a digital circuit that is used to predict the route by which way a branch will go before it is definitively known. The branch predictor major function is improving the flow in the instruction pipeline.) can be seen below.

Given that branch PC has 10bits

14-bit history entries for level-1 and xor with 14 bits of branch PC, so to get the index-2 that ha 2 bit saturating counters

then size of this branch predictor table is 2^14 = 16384 entries