Scalable Parallel Memory Architecture with a Skew Scheme

Tadayuki SAKAKIBARA  Katsuyoshi KITAI  Tadaaki ISOBE  Shigeko YAZAWA  Teruo TANAKA  Yasuhiro INAGAMI  Yoshiko TAMAKI  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E80-D   No.9   pp.933-941
Publication Date: 1997/09/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8532
Type of Manuscript: Special Section PAPER (Special Issue on Architectures, Algorithms and Networks for Massively Parallel Computing)
Category: Computer Architecture
Keyword: 
supercomputer,  vector processor,  interleaved parallel memory,  skew scheme,  memory access conflict,  permanent-concentration,  transient-concentration,  

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Summary: 
We present a scalable parallel memory architecture with a skew scheme by which permanent-concentration-free strides, if any, do not depend on the number of ways in parallel memory interleaving. The permanent-concentration is a kind of memory access conflict. With conventional skew schemes, permanent-concentration-free strides depended on the number of banks (or bank groups) in parallel memory (=number of ways in parallel memory interleaving). We analyze two kinds of cause of conflicts: permanent-concentration occurs when memory access requests concentrate in limited number of banks (or bank groups) in parallel memory, and transient-concentration, when memory access requests transiently concentrate in some banks (or bank groups) in parallel memory. We have identified permanent-concentration-free strides, which are independent of the number of banks (or bank groups) in parallel memory, by solving two concentrations separately. The strategy is to increase the size of address block of shifting address assignment to the parallel memory in order to reduce permanent-concentrations, and make the size of the buffer for each banks (or bank groups) in the parallel memory match the size of address block of shifting in order to absorb transient-concentrations. The skew scheme uses the same size of address block of shifting address assignment for memory systems for different numbers of banks (or bank groups) in parallel memory. As a result, scalability for permanent-concentration-free strides is achieved independent of the number of banks (or bank groups) in parallel memory.