InClassActivity12-sol

# InClassActivity12-sol - 9:33 PM Activity#12(Solution...

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3/2/03 9:33 PM ECSE-2660 Computer Architecture, Networks, & Operating Systems, Spring 2003 Page 1 of 2 Activity #12 (Solution) Activity 12.1 Branch penalties For the following questions, use the following data: Instruction Mix Instruction Type Usage Frequency Loads 15% Stores 11% R-type 50% Jumps 9% Conditional Branches 15% Additional Data 35% of load instructions are followed immediately by an instruction that uses the loaded result (i.e., causes a load-use data hazard that costs an extra cycle); 40% of store instructions are preceeded immediately by an instruction that calculates the value to be stored (i.e., causes a store-use data hazard that costs an extra cycle); Jumps always take 3 cycles Cycle time = 1.5 ns a. (24 points) Calculate the CPI for this machine assuming that the CPU is stalled for 3 cycles for each branch instruction, i.e. branch penalty is 3 cycles. Hint: For such questions that involve averages with weighted trees, it is convenient to use a “decision-tree table”: Instruction Weight Cycles Weighted cycles Loads 0.15 Hazard 0.35 2 0.15 x 0.35 x 2 = 0.1050 No Hazard 0.65 1 0.15 x 0.65 x 1 = 0.0975 Stores 0.11

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InClassActivity12-sol - 9:33 PM Activity#12(Solution...

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