Assignment

Question 1 Background: What is GHz?

A crystal oscillator creates an electrical signal with a precise frequency and outputs a sine wave. Electronic circuitry is used to translate that into a square wave. This pulse drives the microprocessor. The clock rate refers to the frequency at which the signals go through a cycle, and is measured in clock cycles per second (Hz). A Hertz is one cycle per second, or 1/s. It follows that kHz is 103 Hz, MHz is 106 Hz, GHz is 109, and so on. Older computers could only execute one instruction per clock cycle but modern computers may execute multiple instructions per clock cycle.

1. Compare the following 3 processors, executing the same instruction set:
a. P1 3 GHz clock rate, CPI 1.5
b. P2 2.5 GHz clock rate, CPI 1.0
c. P3 4.0 GHz clock rate, CPI 2.2

a. Which processor has the highest performance expressed in instructions per second?

b. If the processors each execute a program in 10 seconds, find the number of cycles and the number of instructions.

c. We are trying to reduce the execution time by 30% but this leads to an increase of 20% in the CPI. What clock rate should we have to get this time reduction? Calculate this for each processor.

2. The results of the SPEC CPU 2006 bzip2 benchmark running on an AMD Barcelona has an instruction count of 2.389E12, an execution time of 750 s, and a reference time of 9650 s.

a. Find the CPI if the clock cycle time is 0.333 ns.

b. Find the SPEC ratio.

c. Find the increase in CPU time if the number of instructions of the benchmark is increased by 10% without affecting the CPI.

d. Find the increase in CPU time if the number of instructions of the benchmark is increased by 10% and the CPI is increased by 5%.

e. Find the change in the SPEC ratio for the change in (d).