PDP-10 Real-Time Multiprogramming System 197007

This document, published in July 1970 by Digital Equipment Corporation, introduces and details the PDP-10 Real-Time Multiprogramming System, an enhancement to the existing PDP-10 computer systems for demanding real-time applications.

Key aspects of the system include:

• Integrated Hardware and Software: The PDP-10 is presented as a complete system, combining its 36-bit central processor (with features like floating-point hardware, multi-level interrupt system, dynamic memory protection, and 366 instructions) with a powerful Real-Time Monitor.
• Enhanced Real-Time Capabilities: The Real-Time Monitor extends the PDP-10's multiprogramming capabilities to deliver higher throughput and faster response times, handling tasks from critical real-time requirements to background time-sharing and batch processing based on their response needs.

• Flexible Task Management:

  • Super Priority Tasks: Can be driven directly by the hardware interrupt system, offering very fast response times (e.g., 6.4µs for a single word transfer using Block-In/Out, ~100µs for full context switching).
  • High Priority Scheduled Jobs: Managed by a software scheduler using "relative urgency" or "least-time-to-go" algorithms, with response times in the 3-30ms range.
  • Background Jobs: Time-sharing and batch processing operate under a background scheduler, providing flexible resource allocation.

• Dynamic Resource Allocation: The system features dynamic memory allocation, eliminating fixed partitions. Real-time jobs can be "locked in core" to prevent swapping and ensure immediate access, while background jobs are swapped as needed, often with I/O and computation overlapping.

• Robust Protection and Communication: The system includes comprehensive fault protection (e.g., against memory violations, program loops, hardware faults) and facilitates communication between real-time and non-real-time jobs through shared data areas and monitor calls.
• Extensive Hardware Support: A wide range of peripherals is supported, including disks, drums, magnetic tapes, data terminals, graphics displays, and interfaces for other DEC computers (PDP-8/9/11/15) and specialized input devices (A/D converters, pulse height analyzers). Multiprocessor configurations are also supported.
• Broad Applications: The PDP-10 Real-Time System is shown to be successful in diverse fields such as high-energy physics, analytical instrumentation, data acquisition, biomedical imaging, industrial control, and hybrid computing, with numerous installations listed across universities and corporations.
• Comprehensive Support: Digital Equipment Corporation provides extensive customer support, including training, detailed documentation, software support specialists, and field service contracts.