性能分析举例 Suppose a processor executes at Clock Rate 200 MHz(5 ns per cycle), Ideal(no misses CPI= 1.1 50%arith/logic, 30%Id/st, 20% control Miss Behavior: 10%of memory operations get 50 cycle miss penalty 1%of instructions get same miss penalty CPI ideal CPi average stalls per instruction 1.1(cycles/ins)+ 030(Data Mops/ins) x0. 10(miss/ Data Mop )x 50 (cycle/miss)] [1(nstMop/ins) x 0.01(miss/InstMop)x 50(cycle/miss) =(11+15+,5) cycle/ins=31 65%(2/ 3. 1)of the time the proc is stalled waiting for memory! AMAT=(1/1.3)x[1+0.01x50]+(0.3/1.3)x[1+0.1X50]=254 2021-2-4 计算机体系结构性能分析举例 § Suppose a processor executes at • Clock Rate = 200 MHz (5 ns per cycle), Ideal (no misses) CPI = 1.1 • 50% arith/logic, 30% ld/st, 20% control § Miss Behavior: • 10% of memory operations get 50 cycle miss penalty • 1% of instructions get same miss penalty § CPI = ideal CPI + average stalls per instruction = 1.1(cycles/ins) + [ 0.30 (DataMops/ins) x 0.10 (miss/DataMop) x 50 (cycle/miss)] + [ 1 (InstMop/ins) x 0.01 (miss/InstMop) x 50 (cycle/miss)] = (1.1 + 1.5 + .5) cycle/ins = 3.1 § 65% (2/3.1) of the time the proc is stalled waiting for memory! § AMAT=(1/1.3)x[1+0.01x50]+(0.3/1.3)x[1+0.1x50]=2.54 2021-2-4 计算机体系结构 46