Altera Nios II Custom Manuel d'utilisateur télécharger pdf (Page 37)

Chapter 4: Implementing a Nios II Custom Instruction in Qsys 4–7

Accessing the Custom Instruction from Software

January 2011 Altera Corporation Nios II Custom Instruction User Guide

Example 4–1. Output of the CRC Design Example Software Run on a NEEK Using the Quartus II Software v10.1 SP1

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Comparison between software and custom instruction CRC32

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System specification

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System clock speed = 62.5 MHz

Number of buffer locations = 16

Size of each buffer = 65535 bytes

Initializing all of the buffers with pseudo-random data

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Initialization completed

Running the software CRC

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Completed

Running the optimized software CRC

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Completed

Running the custom instruction CRC

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Completed

Validating the CRC results from all implementations

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All CRC implementations produced the same results

Processing time for each implementation

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Software CRC = 9928.41 ms

Optimized software CRC = 6414.63 ms

Custom instruction CRC = 137.54 ms

Processing throughput for each implementation

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Software CRC = 0.84 Mbps

Optimized software CRC = 1.31 Mbps

Custom instruction CRC = 60.99 Mbps

Speedup ratio

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Custom instruction CRC vs software CRC = 72.2

Custom instruction CRC vs optimized software CRC = 46.6

Optimized software CRC vs software CRC = 1.5

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Altera Nios II Custom Manuel d'utilisateur Page 37