Consider the following tournament branch predictor that employs a selector with
ID: 3763272 • Letter: C
Question
Consider the following tournament branch predictor that employs a selector with 16K entries (3-bit saturating counters). The selector picks a prediction out of either a global predictor (16-bit global history is XOR-ed with 16 bits of branch PC to index into a table of 2bit saturating counters) or a local predictor (16 bits of branch PC index into level-1, 10 bits of local history are XOR-ed with 10 bits of branch PC to generate the index into level-2 that has 3-bit saturating counters). What is the total capacity of the entire branch prediction system?
Explanation / Answer
The tournament branch predictor has 16K*3 =48K bits
The global predictor has 16+2=18bits.
The local predictor has 10+3 =13 bits.
The total capacity of the entire branch prediction system = 48k bits+ 18 bits+13bits
=48k bits +31bits.
=79k bits.