Initialization of switching networks for use with a scalable coherent

Abstract

The Scalable Coherent Interface (SCI) standard of the Institute of Electrical and Electronics Engineers is intended for fast, high throughput, point-to-point, unidirectional links. It is to serve high-performance multiprocessor systems. A number of key elements are defined as part of the protocol for SCI. These include: (a) command.old which is a bit in transmitted packets for detecting stale packets to discard; (b) idle.cc which is an idle bit to be inserted between packets for detecting lost packets which toggles when the idle bit has circulated around the ringlet; and (c) idle.ac which is an idle bit which toggles when all operational nodes have had an opportunity to transmit. In addition, SCI contemplates the implementation of a number of different types of resets, including power reset, upon read or apparent loss of power for more than a second and linc reset for clearing circuits but not changing error count registers in the system. An implementation of SCI for a switching network which does not contain full agent switches (i.e., switches that have queues), as contemplated by SCI is disclosed which extends the utilization of the above-noted key elements. This implementation provides for a substantial reduction in the complexity, size, power and costs of the network. The network may be expandable in that it can service more than the current number of required operational rings which have at least one scrubber node and may have one or more other functional nodes therein, while handling misrouted packets by providing recirculation conductive connections to all input and output ports of the network that are not connected to such operational rings.