Exercise 7.12 Consider the following three CPU organizations:

CPU SS: A 2-core superscalar microprocessor that provides out-of-order issue capabilities on two functional units (FUs). Only a single thread can run on each core at a time.

CPU MT: A fi ne-grained multithreaded processor that allows instructions from two threads to be run concurrently (i.e., there are two functional units), though only instructions from a single thread can be issued on any cycle.

CPU SMT: An SMT processor that allows instructions from two threads to be run concurrently (i.e., there are two functional units), and instructions from either or both threads can be issued to run on any cycle.

Assume we have two threads X and Y to run on these CPUs that include the following operations:

Thread X Thread Y A1 – takes 2 cycles to execute A2 – depends on the result of A1 A3 – confl icts for a functional unit with A2 A4 – depends on the result of A2 B1 – no dependencies B2 – confl icts for a functional unit with B1 B3 – no dependencies B4 – depends on the result of B2 Assume all instructions take a single cycle to execute unless noted otherwise or they encounter a hazard.

7.12.1 [10] < 7.5> Assume that you have one SS CPU. How many cycles will it take to execute these two threads? How many issue slots are wasted due to hazards?

7.12.2 [10] < 7.5> Now assume you have 1 MT CPU. How many cycles will it take to execute these two threads? How many issue slots are wasted due to hazards?
7.12.3 [10] < 7.5> Assume that you have 1 SMT CPU. How many cycles will it take to execute these two threads? How many issue slots are wasted due to hazards?