KN220 CPU System Maintenance

This document, "KN220 CPU System Maintenance," is a technical guide published by Digital Equipment Corporation in September 1990. It is intended for Digital Customer Services personnel and qualified self-maintenance customers.

The guide provides comprehensive information on the KN220 CPU system, specifically focusing on the KN220 CPU module (M7637-AA) and KN220 I/O module (M7638-AA), which are central to DECsystem 5500 pedestal enclosures running the ULTRIX-32 operating system.

Key areas covered include:

• KN220 Base System Overview: Detailed description of the CPU (R3000 RISC processor, cache memory, main memory system), I/O module (DSSI, SCSI, Ethernet, Q22-bus interfaces), and the H3602-AC CPU I/O panel, including its switches and LEDs. It also covers console serial lines, time-of-year clock, and console security features (passwd, unpriv).
• System Configuration: Guidelines for setting up the KN220 system, including general module order, specific slot assignments for CPU, I/O, and MS220 memory modules, and bulkhead installation. It details the configuration of Q-Bus modules (CONFIGURE command), DSSI (node IDs, cabling, termination), and SCSI interfaces (cabling, node IDs, DIP switches).
• Firmware and Console Operations: Explains the KN220's firmware architecture (residing in EPROMs for R3000 and CVAX), its features (automatic/manual bootstrap, diagnostics, interactive command languages in normal and maintenance modes), and procedures for power-up, halts, and booting ULTRIX-32 or MDM diagnostics. It provides extensive details on normal mode and maintenance mode commands (e.g., boot, dump, examine, setenv, test, CONFIGURE, DEPOSIT, SHOW), including their syntax, qualifiers, and arguments.
• Troubleshooting and Diagnostics: Describes the ROM-based diagnostics used for the CPU, memory, Ethernet, SCSI, and DSSI subsystems. It outlines general troubleshooting steps, acceptance testing procedures, and specific diagnostics for isolating memory failures and testing various interfaces using ROM-based tests (T command) and utilities (FE utility). It also lists and explains system halt, console error, and VMB error messages.
• Appendices (Reference Information):
  • ULTRIX-32 Exerciser and uerf Commands: Summarizes on-line functional testing tools and error log commands specific to the ULTRIX-32 operating system.
  • Address Assignments: Provides detailed physical and I/O address space maps for the R3000 and CVAX processors.
  • KFQSA Configuration: Specific instructions for installing and programming the KFQSA storage adapter, including setting node IDs and unit numbers for DSSI devices.
  • Prestoserve Software: Explains data recovery procedures for the NVRAM cache on the CPU board using dc commands (/SAVE, /RESTORE, /ZERO) after abnormal system shutdowns.
  • Field-Replaceable Units (FRUs): Lists major components with their part numbers for easy identification and replacement.
  • Related Documentation: Provides a list of other relevant technical manuals.