Rainbow Technical Manual Addendum for Models PC100-A, PC100-B, and Rainbow 100+

This document serves as a technical manual addendum for service engineers and technicians, detailing the design, operation, and architecture of Digital Equipment Corporation's Rainbow PC100-A, PC100-B, and Rainbow 100+ personal computers.

The manual provides:

• System Overview: A general description of the Rainbow models, highlighting their dual-processor architecture (8088 and Z80A microprocessors) that supports CP/M-86/80 or MS-DOS operating systems. It outlines the basic units of the computer (system unit, monitor, keyboard) and their standard features, including memory (RAM expandable to 896KB), diskette drives (800KB), optional Winchester hard disk (10MB), and various I/O ports.
• Specifications: Detailed technical specifications for the system unit, power supply, monochrome and color monitors, keyboard, RX50 dual-diskette drive, RD51 hard disk drive, and memory/graphics options.
• Operating Information: Guidance on handling diskettes, power-up procedures (including self-tests and auto-boot), and interpretation of nonfatal and fatal error messages. It extensively covers the "Set-Up" features, allowing users to customize computer characteristics such as display settings, terminal emulation (VT52/ANSI), communication protocols, baud rates, language selection, and auto-boot options, with instructions on saving these settings.
• Technical Descriptions: In-depth functional and physical descriptions of the PC100-B system module, including its processor interaction, memory organization (shared/unshared RAM, ROM, NVM, video RAM), I/O decoders, interrupt handling, video processor for display attributes and modes, and the multiprotocol serial controller (MPSC) for communications and printer control.
• Hard Disk Controller: A dedicated chapter on the Winchester hard disk controller, detailing its interface with the 8088 processor, the WD1010 controller chip, data transfer rates, programming registers, and track/sector formats.
• Power Supply and Fan Assembly: Description of the H7842-D power supply, its role in AC-to-DC conversion, and its control/sensing circuits for overcurrent/overvoltage protection.
• Diagnostics: Appendices include a comprehensive parts list, character generator ROM codes, and a guide to internal ROM-resident and diskette-resident diagnostic tests, complete with error messages and troubleshooting actions.