VAXft Systems System

This document provides a technical description of the VAXft system, a fault-tolerant VAX computer designed for high availability and reliability. The system features a dual-zone architecture, with two identical sets of components housed in separate cabinets. These zones operate in "lockstep" mode, ensuring continuous operation and no downtime even in the event of a single component failure, as the remaining zone seamlessly takes over while repairs are made to the faulty one.

Key hardware components are modular and accessible from the front for simplified maintenance. Each zone contains a Central Processor Unit (CPU) module (KA520 or KA550), Memory Modules (MS520) with error correction, a System I/O Controller (KFE52) for mass storage, network I/O (Ethernet), and console functions, and optional Communication Controller (DEC WANcontroller 620) modules for synchronous communications with failover capabilities. The system employs duplicated cross-link cables for inter-zone communication and various internal buses for module interconnectivity.

Power is managed by an AC system with an Uninterruptible Power Supply (UPS) in each zone, allowing for controlled shutdowns during power outages of up to 30 minutes for internal components. Cooling is actively monitored, and fan speeds adjust to maintain optimal operating temperatures. Fault detection is achieved through the dual-zone design, with visual indicators on logic modules highlighting failures.

The document details two primary system configurations: an entry-level system with integrated mass storage, and an expanded system that utilizes additional cabinets for increased shadowed mass storage. A system console provides full control for booting, maintenance, diagnostics, and remote access.