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The POWER8i processor is the latest RISC (Reduced Instruction Set Computer) microprocessor from IBM. It is fabricated using the company's 22-nm Silicon on Insulator (SOI) technology with 15 layers of metal, and it has been designed to significantly improve both single-thread performance and single-core throughput over its predecessor, the POWER7 A processor. The rate of increase in processor frequency enabled by new silicon technology advancements has decreased dramatically in recent generations, as compared to the historic trend. This has caused many processor designs in the industry to show very little improvement in either single-thread or single-core performance, and, instead, larger numbers of cores are primarily pursued in each generation. Going against this industry trend, the POWER8 processor relies on a much improved core and nest microarchitecture to achieve approximately one-and-a-half times the single-thread performance and twice the single-core throughput of the POWER7 processor in several commercial applications. Combined with a 50% increase in the number of cores (from 8 in the POWER7 processor to 12 in the POWER8 processor), the result is a processor that leads the industry in performance for enterprise workloads. This paper describes the core microarchitecture innovations made in the POWER8 processor that resulted in these significant performance benefits.

Abstract

The continuing importance of game applications and other numerically intensive workloads has generated an upsurge in novel computer architectures tailored for such functionality. Game applications feature highly parallel code for functions such as game physics, which have high computation and memory requirements, and scalar code for functions such as game artificial intelligence, for which fast response times and a full-featured programming environment are critical. The Cell Broadband Enginee architecture targets such applications, providing both flexibility and high performance by utilizing a 64-bit multithreaded PowerPCt processor element (PPE) with two levels of globally coherent cache and eight synergistic processor elements (SPEs), each consisting of a processor designed for streaming workloads, a local memory, and a globally coherent DMA (direct memory access) engine. Growth in processor complexity is driving a parallel need for sophisticated compiler technology. In this paper, we present a variety of compiler techniques designed to exploit the performance potential of the SPEs and to enable the multilevel heterogeneous parallelism found in the Cell Broadband Engine architecture. Our goal in developing this compiler has been to enhance programmability while continuing to provide high performance. We review the Cell Broadband Engine architecture and present the results of our compiler techniques, including SPE optimization, automatic code generation, single source parallelization, and partitioning.