Question

1.     The design team for a simple, single-issue processor is choosing between a pipelined or

Non-pipelined implementation. Here are some design parameters for the two possibilities:

Parameter Pipelined Version Non-Pipelined Version

Parameter                                        Pipelined Version             Non-Pipelined Version

Clock Rate                                        500MHz                              350 MHz

CPI for ALU instructions                   1                                         1

CPI for Control                                  2                                         1

instructions

CPI for Memory                                2.7                                      1

instructions

For a program with 80% ALU instructions, 10% control instructions and 10% memory

instructions, which design will be faster? Give a quantitative CPI average for each case.

Answer 1

The selection between Pipelined Version Non-Pipelined Version is given as follows:

Average CPI for Pipelined Version = (0.8*1 + 0.1*2 + 0.1*2.7) = 1.27

Average CPI for Non-Pipelined Version = (0.8*1 + 0.1*1 + 0.1*1) = 1

CPU execution time for Pipelined version = /(500 Mhz) = 2.5ns

CPU execution time for Non-Pipelined version = 1.0/(350 Mhz) = 2.8ns

The pipelined version is faster.

So, we can say that the pipelined version is faster as it takes 2.5 ns compared to non-pipelined version that takes 2.8 ns.

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