RA81 Disk Drive

This user guide provides comprehensive instructions for the installation, checkout, and operation of the RA81 Disk Drive. Primarily intended for RA81 users, with installation procedures detailed for qualified field service personnel, the manual describes the RA81 as a random-access, moving-head disk drive with non-removable media contained within a sealed Head/Disk Assembly (HDA) designed for data protection and hardware dependability. It offers a substantial data storage capacity of 456 megabytes in 16-bit word format.

Key performance features include a 17.4 megabit per second peak transfer rate, 28 ms average positioning rate, and 8.3 ms average rotational latency. Data integrity is ensured through protected media, a microprocessor-controlled servo system, and automatic error correction. The hardware is characterized by simple modular construction, a rugged design, and extensive microcode diagnostics, managed by a dual-microprocessor control system. The RA81 connects to controllers via the Standard Disk Interconnect (SDI) bus, supporting configurations with multiple drives per controller or a dual-port arrangement for time-shared access by two controllers.

The document covers detailed installation steps, including site preparation (environmental, cleanliness, floor loading, heat dissipation, power, and safety), equipment unpacking, cabinet leveling, removal of internal shipping brackets, and procedures for connecting cabinets, external and internal SDI cabling, and programming the drive unit address plug. Diagnostic checkout instructions detail how to apply power and run drive-resident diagnostics using a field service diagnostic terminal. Operational guidelines explain the control panel switches and indicators (RUN/STOP, FAULT, UNIT/READY, WRITE PROT, A and B Port Select), circuit breakers, drive spin-up and spin-down processes, and customer care routines, such as air filter inspection and replacement.

A change notice (EK-ORA81-UG-CN2) updates the guide, notably clarifying that while a dual-port arrangement connects two controllers, a drive can only be on-line to one controller at a time, requiring a 100- to 200-millisecond microcode switch-over process. It also details hardware revisions (Revision 8 as of April 1, 1986) aimed at improving quality and reliability, covering changes to the lower chassis configuration, front bezel, detent latch, operator control panel, replacement of EMI spring fingers with gaskets, redesigns of motor brake and belt tension components, and specific power supply requirements (H7660 A/B revision 'F' or H7660 C/D). The notice also provides updated unpacking procedures and electrical plug/receptacle figures.