The implementation of low latency communication primitives in the SNOW prototype

This paper describes the implementation of a low latency protected message passing facility and a low latency barrier synchronization mechanism for an experimental, tightly-coupled network of workstations called SNOW: SNOW uses multiprocessing SPARC 20s, running Solaris 2.4, as computing nodes, and uses semi-custom network interface cards (NICs) that connect these nodes in a 212 Mbits/sec. unidirectional ring. The NICs include field-programmable gate array logic devices that allow for experimentation with the nature and level of hardware support for tight coupling. The one way protected message passing latency on the SNOW prototype for a 64-byte message is about 9 μsecs., comparable to latencies of low-end to medium range multiprocessors