Abstract: The Scalable Coherent Interface (SCI) standard of the Institute of Electrical and Electronics Engineers is intended for fast, high throughput, unidirectional links to high performance microprocessor systems. Key elements of the protocol for SCI include: (a) a "new/stale" bit which is generated in a data packet for detecting stale packets to discard; (b) a scrubber node in each operational ring of an SCI network which toggles "new/stale" bits from a "new" state to a stale state when they are received at the scrubber node. In addition, valid ring identity code bits are used to identify operational rings and target identity code bits are used to identify the intended designated target mode of each packet. Packets are transmitted from input ports to output ports of the switches and through operational rings of the network that are connected until each of the packets reaches a designated target node.

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 to high-performance multiprocessor systems. Key elements of the protocol for SCI are the (a) idle.cc which are idle bits circulation to be inserted between packets transmitted in an SCI network for detecting lost packets which toggles when the idle bit circulation has circulated around the ringlet; and (b) idle.ac, or allocation bit which is a bit in a group of transmitted idle bits which toggles when all operational nodes in an SCI network have had an opportunity to transmit their data packets. All switches accumulate transitions of the allocation bits to a value that is different from the current remembered allocation value on each enabled input port. If the network is out of allocation bit synchronization at a switch when a second transition of allocation bit occurs on an input port of the switch, the transition is ignored.