The Gemini interconnect is a dual technology (optical and electrical) interconnection network designed for use in tightlycoupled multicomputer systems. It consists of a circuit-switched optical data path in parallel with a packet-switched electrical control/ data path. The optical path is used for transmission of long data messages and the electrical path is used for switch control and transmission of short data messages. This paper describes the architecture of the interconnection network and related communications protocols. Fairness issues associated with network operation are addressed and a discrete-event simulation model of the entire system is described. Network performance characteristics derived from the simulation model are presented. The results show significant performance benefits when using virtual output queuing and quantify the tradeoffs between throughput and fairness in the system.
This paper presents the design and initial analysis of an optically interconnected multiprocessor based on the use of VCSELs (Vertical Cavity Surface Emitting Laser) and free-space optical interconnects.The design is oriented to applications where the performance is bandwidth limited i n c onventional multiprocessors. The processor interconnection network is based o n a physical ring topology which is logically con gured a s a multiring. Two alternative communications protocols are p r esented and the performance p r operties associated with a packet-based Go-Back-N protocol are discussed. Relationships between bit error rate and performance are p r ovided.
Existing fair scheduling schemes have focused primarily on scheduling multiple ows to a single output. The limited work that has focused o n s c h e duling multiple ows to multiple outputs has assumed a non-blocking, slotted-time, cell-based network with a centralized c ontroller. This paper presents a fair scheduler suitable for use in bu erless circuit-switched blocking networks operating with distributed, asynchronous controllers and variable length messages. We begin by describing the potential for starvation in the Gemini interconnect network, an optical, circuit-switched network. A proposed distributed fair scheduler is presented and shown to solve this problem. The tradeo s and limitations of performing many-to-many fair scheduling in general, and that of our fair scheduler in particular, are discussed.
The Gemini interconnect is a dual technology (optical and electrical) interconnection network designed for use in tightly-coupled multicomputer systems. It consists of a circuit-switched optical data pa t h i n p arallel with a packet-switched electrical control/data path.Here, we present quantitative measurements of optical data path operation from the physical implementation, as well as a discrete-event simulation model of the entire interconnect that includes visualization capabilities. Performance analyses of several aspects of system operation are developed f r om the simulation model.
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