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1997 Fiscal Year Final Research Report Summary

Research on a Very Large Data Path processor

Research Project

Project/Area Number 07458052
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field 計算機科学
Research InstitutionUniversity of Tokyo

Principal Investigator

TANAKA Hidehiko  The University of Tokyo, Graduate School of Engineering, 大学院・工学系研究科, 教授 (60011102)

Project Period (FY) 1995 – 1997
Keywordsdataflow anaysis / VLDP / branch handling / speculative execution / dynamic prefetch / address prediction / data traffic / ILP
Research Abstract

In this research, we took a close look at parallelism extraction, handling of control dependencies, and enhanced memory system, which could be the key technologies of Very Large Data Path (VLDP) architecture. The outcome we gained are as follows.
Firstly, we examined the characteristics of parallelism restricted by control dependencies and data dependencies : we found that the VLDP architecture can achieve dozens of times as much performance as conventional scalar processors can, when we have both the perfect branch predictor and the complete memory system.
Secondly, we examined suitable branch handling for the VLDP architecture. This branch handling needs to treat simultaneously plural control flow and needs to fetch instructions speculatively across many branches. For this purpose, we proposed a new branch predictor named multi-level branch predictor and examined its behavior.
Thirdly, we improved a memory system based on the cache mechanism by utilizing a newly proposed data prefetch algorithm that predicts a referenced address based on the evaluation of a linear function. We confirmed this new system lessens overhead of memory references. Moreover we examined the traffic between the memory and the datapath, which tends to be a bottleneck for high performance processors. We showed that this traffic is reduced to less than half of conventional scheme when the VLDP architecture utilizes the direct data transfer among the remarkable number of ALUs.
From these results, technological issues of VLDP architecture are made clear and we confirmed the possibility of performance improvement.

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Published: 1999-03-16  

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