Computer Architecture Consider that a program consists of 30% integer instructio

Question

Computer Architecture

Consider that a program consists of 30% integer instructions and 70% floating point instructions. You have a processor that can process 2 million instructions per second (MIPS) regardless the instruction type. But, you want to optimize the processor design like below: Design choice 1: Redesign the integer processing unit that can process instructions at 6 MIPS Design choice 2: Redesign the floating point processing unit that can process instructions at 3.2 MIPS. Which design choice would you choose if you can choose only one option? Justify your choice by presenting the expected speedup of each design.

Explanation / Answer

Given ,

Number of integer instructions is = 30 %

Number of floating point instructions is = 70 %

Processor speed is = 2 MIPS

Design choice 1 :

Given speed of integer processing unit is = 6 MIPS

Now speed up is = Time taken after upgradation / Time taken before upgradation

Time taken after upgradation is = 30 % * Time to process integer instructions +

70 % * Time to process floating point instructions

= 30 % * 6 + 70 % * 2

= 1.8 + 1.4 = 3.2

Here Time taken before upgradation is = 2

Hence Speedup = 3.2 / 2 = 1.6.

Design choice 2 :

Given speed of floating point processing unit is = 3.2 MIPS

Now speed up is = Time taken after upgradation / Time taken before upgradation

  Time taken after upgradation is = 30 % * Time to process integer instructions +

70 % * Time to process floating point instructions

= 30 % * 2 + 70 % * 3.2

= 0.6 + 2.24 = 2.84

Here Time taken before upgradation is = 2

  Hence Speedup = 2.84 / 2 = 1.42.

Hence Design 1 is the best option.

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