RA81 Disk Drive User Guide

This document is a User Guide for the RA81 Disk Drive (EK-ORA81-UG-001), published by Digital Equipment Corporation in 1982.

The RA81 Disk Drive is described as a random-access, moving-head disk drive with non-removable media (a sealed Head/Disk Assembly or HDA), designed for increased data protection and dependability.

Key characteristics and features include:

• Storage Capacity: 456 megabytes (in 16-bit word format).
• Connectivity: Connects to controllers via the Standard Disk Interconnect (SDI) bus, supporting multi-drive configurations (up to three drives per cabinet) and dual-port access for time-shared use by two controllers.
• Performance: Offers a peak transfer rate of 17.4 megabits per second, an average positioning rate of 28 ms, and a rotational speed of 3600 rpm.
• Internal Design: Self-contained with built-in cooling and DC power supply. It features a dual-microprocessor control system (master and slave) and extensive microcode diagnostics for error detection and fault isolation.
• Data Integrity: Enhanced by protected media, microprocessor-controlled servo, and automatic error correction.

The guide provides instructions on:

• Installation (Chapter 2): Covers site preparation (environmental, cleanliness, floor loading, power), equipment unpacking, cabinet connection, SDI cabling, and programming the drive unit address plug. This chapter is primarily for qualified field service personnel.
• Operating Instructions (Chapter 3): Details the functions of the front-panel switches and indicators (RUN/STOP, FAULT, UNIT/READY, WRITE PROT, Port A/B select), circuit breakers, basic drive operation (spin-up/spin-down), and routine customer care (e.g., air filter maintenance).
• Diagnostic Terminal Instructions (Appendix A): Describes how to use a field service diagnostic terminal for advanced troubleshooting and running internal diagnostics.