PDP-11/70 Multiprocessor

This document describes the PDP-11/70 Multiprocessor System, designed for enhanced availability and performance through symmetrical multiprocessing. The system consists of two (expandable to four for PDP-11/74) modified KB11-C processors, which share a common, multiported MOS memory (MKAll) ranging from 64KB to 16MB with Error Correction Coding (ECC) and battery backup. All processors are controlled by a single operating system (RSX-11M+).

Key components and their functions include:

• Interprocessor Interrupt and Sanity Timer (IIST) Subsystem: Facilitates communication between processors, enabling task rescheduling through interrupts and boot requests. Its Sanity Timer detects faulty processors, halting them and locking their Unibus to prevent system disruption. A BOOT/IIST Panel allows operators to monitor processor status, manually boot, select power-up actions, and configure the system.
• Modified KB11-C Processors: Include specific features for multiprocessor operation such as Cache Flush (invalidating cache data), Cache Bypass (forcing memory references directly to main memory for shared data), and an ASRB instruction to implement memory locks, ensuring exclusive access to critical shared data.
• Massbus Operation: Utilizes RH70 Massbus controllers and RH01 Dual-Port Adapters, allowing Massbus devices to be dual-accessed (shared or switched) between processors for resource optimization and high availability.
• DT07 Shared Unibus Switch: Enables single-ported Unibus peripherals to be switched between different processors, offering flexibility for device sharing, system backup, and dynamic reconfiguration. It supports failsoft operations using a watchdog timer.
• DB11-A Bus Repeater: Extends the Unibus capacity, allowing more devices to be connected without significant impact on bus cycle time.
• Remote Serial Diagnostic Console (Optional): Provides an alternative to the physical switch console, offering remote control and diagnostic capabilities for individual processors via ASCII commands.

The document details the functional descriptions of these components, their interfaces, operating controls, and programming aspects, with a focus on system operation, installation, maintenance, and troubleshooting.