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Dissertation/Thesis Abstract

Decoupled Vector-Fetch Architecture with a Scalarizing Compiler
by Lee, Yunsup, Ph.D., University of California, Berkeley, 2016, 157; 10151006
Abstract (Summary)

As we approach the end of conventional technology scaling, computer architects are forced to incorporate specialized and heterogeneous accelerators into general-purpose processors for greater energy efficiency. Among the prominent accelerators that have recently become more popular are data-parallel processing units, such as classic vector units, SIMD units, and graphics processing units (GPUs). Surveying a wide range of data-parallel architectures and their parallel programming models and compilers reveals an opportunity to construct a new data-parallel machine that is highly performant and efficient, yet a favorable compiler target that maintains the same level of programmability as the others.

In this thesis, I present the Hwacha decoupled vector-fetch architecture as the basis of a new data-parallel machine. I reason through the design decisions while describing its programming model, microarchitecture, and LLVM-based scalarizing compiler that efficiently maps OpenCL kernels to the architecture. The Hwacha vector unit is implemented in Chisel as an accelerator attached to a RISC-V Rocket control processor within the open-source Rocket Chip SoC generator. Using complete VLSI implementations of Hwacha, including a cache-coherent memory hierarchy in a commercial 28 nm process and simulated LPDDR3 DRAM modules, I quantify the area, performance, and energy consumption of the Hwacha accelerator. These numbers are then validated against an ARM Mali-T628 MP6 GPU, also built in a 28 nm process, using a set of OpenCL microbenchmarks compiled from the same source code with our custom compiler and ARM's stock OpenCL compiler.

Indexing (document details)
Advisor: Asanovic, Krste
Commitee: Nikolic, Borivoje, Patterson, David A., Wright, Paul K.
School: University of California, Berkeley
Department: Electrical Engineering and Computer Sciences
School Location: United States -- California
Source: DAI-B 78/01(E), Dissertation Abstracts International
Subjects: Computer science
Keywords: Computer architecture, Hwacha vector-fetch architecture, RISC-V, Scalarizing compiler, Vector processor
Publication Number: 10151006
ISBN: 978-1-369-05770-6
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