S3.mp (Sun's Scalable Shared memory MultiProcessor)is a research project to demonstrate a low overhead, high throughput communication system that is based on cache coherent distributed shared memory (DSM). S3.mp uses distributed directories and point-to-point messages that are sent over a packet switched interconnect fabric to achieve scalability over a wide range of configurations.
S3.mp uses a new CMOS serial link technology that achieves transmission rates >lGbitlsec and that is directly integrated into a packet router chip. Unlike other DSM systems, S3.mp can be spatially distributed over a local area via fiber optic links. This capability allows S3.mp to interconnect clusters of workstations to form multiprocessor workgroups that efficiently share memory. processors andI 1 0 devices. Multichip module technology, the integrated arbitrary topology router, fast serial linh, and a DSM system that is integrated into the memory controller allow compact, massively parallel S3.mp systems.
Abstract. This paper presents the results for the verification of the S3.mp cache coherence protocol. The S3.mp protocol uses a distributed directory with limited number of pointers and hardware supported overflow handling that keeps processing nodes sharing a data block in a singly linked list. The complexity of the protocol is high and its validation is challenging because of the distributed algorithm used to maintain the linked lists and the non-FIFO network. We found several design errors, including an error which only appears in verification models of more than three processing nodes, which is very unlikely to be detected by intensive simulations. We believe that methods described in this paper are applicable to the verification of other linked list based protocols such as the IEEE Scalable Coherent Interface.
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