FCO CI750-1005 Rev B, Cluster of 6 CI/HSC nodes on SC008

This Field Change Order (FCO CI750-1005 Rev B) addresses issues in VAXclusters with six or more CI/HSC nodes connected via an SC008 Star Coupler. The problem manifests as CI-PATH NO RSP, NAK, ARB-TIMEOUTS, and VC-CLOSURE errors, primarily due to adjacent-node collision and arbitration issues.

The solution involves installing the L0118 Rev B* link module, which supersedes L0100 Rev D* modules, and allows L0100 Rev E* to coexist (except in environments with more than 16 nodes). The L0118 module incorporates several design changes to mitigate these problems, including:

• Extending the basic quiet-slot from 7 to 10 ticks to prevent collisions.
• Fixing high/low-priority arbitration logic to prevent biasing.
• Extending ACK-turnaround time for reliable packet reception.
• Correcting SYNC-DETECT issues and extending trailer transmit time.
• Enhancing arbitration status reporting and fixing CRC-count reset failures.

Installation requires a cluster shutdown, as the new "10-TICK-MODE" is incompatible with older L0100-D1 and "7-TICK-MODE" operations; mixed modes can severely impact performance. The procedure involves replacing existing link modules with the L0118 (Rev B), setting specific jumpers and switches to either "7-TICK COMPATIBLE" mode (for initial testing) or "10-TICK INCOMPATIBLE" mode (for final operation after all nodes are upgraded), and running offline diagnostics. Electrostatic discharge precautions are necessary. The estimated installation time is 1 hour per node.