In Chapter 5.7 of CSAPP, author list out the throughput boundary of Intel Core i7 Haswell while executing the operation Integer addition and multiplication, floating points addition and multiplication. Here is the function units list.enter image description here The author also pointed out the equation was throughput boundary = Capacity/Issue. Here is the data.enter image description here

I wonder how did the result equals to 0.5.enter image description here Because if the capacity is 2 and the issue is 1, it should be 2 right?

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1 Answer 1


You confused the definition of maximum throughput and throughput bound:

  • Maximum throughput = Capacity/Issue time
  • Throughput bound "gives a minimum bound for the CPE based on the maximum rate at which the functional units can produce results" (quoted from CSAPP). So throughput bound is the theoretical minimum CPE(Cycles per Element) caused by maximum throughput. Throughput bound = 1/maximum throughput.

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