PDP-11 Architecture Handbook

This document provides a comprehensive overview of the Digital Equipment Corporation (DIGITAL) PDP-11 computer family, emphasizing its consistent 16-bit architecture that ensures software compatibility across various models and technological generations. The handbook serves as a guide for both technical users seeking in-depth architectural details and new users requiring a tutorial introduction.

Key architectural elements detailed include:

• Data Representation: Covers integer (8-bit bytes and 16-bit words), floating-point (32-bit single-precision and 64-bit double-precision), and string (character and decimal) data types, manipulated by the basic PDP-11 Instruction Set, Floating-Point Instruction Set (FP-11), and Commercial Instruction Set (CIS).
• Addressing Modes and Registers: Explains the use of eight 16-bit general-purpose registers (including the Program Counter and Stack Pointer) and various addressing techniques (e.g., register, autoincrement, index, and PC-relative modes) for efficient data access.
• Instruction Sets: Describes the standard PDP-11 instruction set (categorized into single-operand, double-operand, branch, jump/subroutine, trap, miscellaneous, and condition code operations), and optional instruction sets like FP-11 and CIS.
• Traps and Interrupts: Outlines the mechanisms for handling system errors (processor traps due to power failures, hardware/software errors, or illegal instructions) and external device requests (interrupts) to maintain system integrity and facilitate efficient I/O.
• Memory Management and Bus Structures: Details the Memory Management Unit (MMU) for virtual-to-physical address translation, protection of operating system software, and extended memory addressing. It also covers the UNIBUS and LSI-11 Bus structures, their arbitration, data transfer protocols, and control functions.

The document also traces the evolution of the PDP-11 family, from its initial release in 1970 and its growth from the PDP-8, through various milestones up to 1982, including the development of LSI-11 microcomputers, advanced processors like the PDP-11/70 and MICRO/J-11, and the introduction of peripherals, networking, and a wide range of operating systems that leverage the compatible architecture.