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Title: A quantitative performance evaluation of SCI memory hierarchies
Author: Hexsel, Roberto A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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The Scalable Coherent Interface (SCI) is an IEEE standard that defines a hardware platform for scalable shared-memory multiprocessors. SCI consists of three parts. The first is a set of physical interfaces that defines board sizes, wiring and network clock rates. The second is a communication protocol based on undirectional point to point links. The third defines a cache coherence protocol based on a full directory that is distributed amongst the cache and memory modules. The cache controllers keep track of the copies of a given datum by maintaining them in a doubly linked list. SCI can scale up to 65520 nodes. This dissertation contains a quantitative performance evaluation of an SCI-connected multiprocessor that assesses both the communication and cache coherence subsystems. The simulator is driven by reference streams generated as a by-product of the execution of "real" programs. The workload consists of three programs from the SPLASH suite and three parallel loops. The simplest topology supported by SCI is the ring. It was found that, for the hardware and software simulated, the largest efficient ring size is between eight and sixteen nodes and that raw network bandwidth seen by processing elements is limited at about 80Mbytes/s. This is because the network saturates when link traffic reaches 600-700Mbytes/s. These levels of link traffic only occur for two poorly designed programs. The other four programs generate low traffic and their execution speed is not limited by interconnect nor cache coherence protocol. An analytical model of the multiprocessor is used to assess the cost of some frequently occurring cache coherence protocol operations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available