RSX-11M - PDP-11/70 MULTIPROCESSING SYSTEM FUNCTIONAL SPECIFICATION

This document details the RSX-11M - PDP-11/70 Multiprocessing System Functional Specification, describing a tightly coupled, symmetrical multiprocessor product with 2-4 PDP-11/70 CPUs and RSX-11M operating system software. The primary focus is on enhanced system availability, performance, and maintainability.

Key features include:

• System Architecture: A single shared RSX-11mP Executive manages all processors and shared resources (memory, I/O devices). The system supports distributed I/O, allowing any program on any processor to use any I/O device.
• Availability: Achieved through redundant hardware (CPUs, memory, data paths, peripherals), on-line reconfiguration capabilities (allowing faulty components to be isolated and repaired without system downtime), and robust fault isolation features in hardware (e.g., multiport memory, switchable UNIBUSES, Interprocessor Interrupt & Sanity Timer - IIST). The system aims for a significant reduction in unavailability and improvement in Mean Time Between Failures (MTBF).
• Performance: Enhanced through concurrent task execution across multiple CPUs, automatic utilization of redundant resources, CPU and I/O load leveling, and improved disk seek operations. Special hardware modifications and software mechanisms (e.g., cache flush, virtual page bypass, force bypass, ASRB instruction for semaphores) are implemented to ensure cache consistency in the shared memory environment.
• Maintenance: Supported by powered-up repairability, allowing off-line maintenance while the critical system functions continue. Comprehensive error logging provides detailed information for fault diagnosis, and system-loadable and stand-alone diagnostics facilitate troubleshooting.
• Hardware Components: Key components include modified PDP-11/70 processors (with cache consistency features), Multiport MOS Memory (MKA11) with independent power supplies and programmable port control, an Interprocessor Interrupt and Sanity Timer (IIST), a Time-Of-Day (TOD) Clock with battery backup, and multiport/multiaccess I/O devices (e.g., MASSBUS devices, UNIBUS switches) designed for fault tolerance and symmetry.
• Software Components: The RSX-11mP Executive handles multiprocessor interactions, manages cache consistency, and facilitates on-line reconfiguration. A multiprocessor bootstrap module (M9301-mP) manages system boot-up, and a suite of diagnostics (on-line, user-mode, and stand-alone) is provided.

The design emphasizes using existing hardware and software where possible, leveraging the PDP-11/70's multi-bus structure and RSX-11M's real-time capabilities for a high-availability, high-performance solution in critical applications.