TABLE OF CONTENTS

The advent of the PowerPC microprocessor with AltiVec technology made general-purpose microprocessors into viable candidates for high-end, signal-processing applications. The original PowerPC, which Motorola and IBM had jointly designed, combined relatively low power for a GP micro with computational performance well beyond what its clock frequencies could indicate. However, the G4 generation of AltiVec microprocessors, with their super-scalar architecture and integrated Single Instruction, Multiple Data (SIMD) capabilities, are what made the architecture competitive for digital signal processing (DSP).

Today there are a number of general-purpose microprocessor architectures, while not designed for high-end signal processing, which might provide the processing performance required for complex radars, leading-edge semiconductor inspection systems, and other such demanding applications. Nevertheless, how well does each really perform as a digital signal processor? Additionally, how do these contenders compare for different kinds of operations on various length vectors running out of different levels of a memory subsystem?

To answer this question, engineers from SKY Computers developed simple benchmarks to gauge the memory bandwidth and computational performance of the Motorola 7447 PowerPC, IBM 970 PowerPC, AMD Opteron, and Broadcom MIPS-based 1250 chips for common types of radar and signal intelligence.

The bottom line of those benchmarks completed to date is that the PowerPC with AltiVec produces impressive computational performance compared to the other processors considered. Motorola, now Freescale, has updated the performance of the 74xx several times since its introduction. Apple uses the 74xx in its G4 systems, as well as in its laptop computers. Apple laptops currently in the market are running nearly five times faster than the first G4 systems, due to a redesign of the PowerPC 7400’s pipeline for the PowerPC 7445/7455. Further, IBM is now also shipping a PowerPC with AltiVec capability based on their power architecture.

Yet, despite the strengths of AltiVec, the benchmarks revealed that the alternative processors offer some interesting capabilities for particular types of signal processing. These include applications where memory bandwidth, for example, may be more important than sheer speed, or where parts count is limited.

The basic benchmarks run were:

* Memory-read bandwidth
* Vector multiply
* Fast Fourier Transform (FFT)
* Basic signal processing

Table 1 lists the basic characteristics of the benchmarked microprocessors. The following figures indicate a sampling of the results. Some of the results were exactly as expected, but some surprises also emerged.

The advent of the PowerPC microprocessor with AltiVec technology made general-purpose microprocessors into viable candidates for high-end, signal-processing applications. The original PowerPC, which Motorola and IBM had jointly designed, combined relatively low power for a GP micro with computational performance well beyond what its clock frequencies could indicate. However, the G4 generation of AltiVec microprocessors, with their super-scalar architecture and integrated Single Instruction, Multiple Data (SIMD) capabilities, are what made the architecture competitive for digital signal processing (DSP).

Today there are a number of general-purpose microprocessor architectures, while not designed for high-end signal processing, which might provide the processing performance required for complex radars, leading-edge semiconductor inspection systems, and other such demanding applications. Nevertheless, how well does each really perform as a digital signal processor? Additionally, how do these contenders compare for different kinds of operations on various length vectors running out of different levels of a memory subsystem?

To answer this question, engineers from SKY Computers developed simple benchmarks to gauge the memory bandwidth and computational performance of the Motorola 7447 PowerPC, IBM 970 PowerPC, AMD Opteron, and Broadcom MIPS-based 1250 chips for common types of radar and signal intelligence.

The bottom line of those benchmarks completed to date...