KL10-Based Technical Manual

This document, "KL10-Based Technical Manual," EK-OKL10-TM-002, provides a comprehensive system-level technical description of the DECsystem-10/DECSYSTEM-20 computer, specifically focusing on the KL10-R-based machine. It integrates hardware and software aspects, offering overviews of timesharing/batch operations and system features.

The manual is structured into four main chapters and an appendix:

1. Introduction: Introduces the DECsystem-10/DECSYSTEM-20 as a large-scale, high-performance system featuring a KL10-R central processing unit (CPU). It highlights key features such as large-capacity MOS memory (at least 512K words, up to 1.5 megawords internal and 1.5 megawords external), internal data channels, Massbus controllers, and an integral PDP-11/40 front-end processor. The system supports extended addressing and provides service for 40 to 80 users, protecting investments in the TOPS-20 operating system.

2. System Features: Details the core capabilities of the DECsystem-10/DECSYSTEM-20.

   • CPU: Uses high-speed ECL logic and a microprogrammed instruction set of 398 instructions, designed for flexibility and efficiency (shorter, faster assembly programs). It supports direct and indirect addressing, various arithmetic modes (fixed-point, floating-point), byte manipulation, and logical operations.
   • Memory System: Includes MOS memory, Direct Memory Access (DMA) for efficient transfers, and a 150-nanosecond access time data cache (with a high hit rate to improve effective access time).
   • Processor Modes: Operates in User and Executive modes with submodes, managed by a page map that controls access and protection.
   • I/O and Interrupts: Features a direct I/O over the EBus for low-speed devices, and Channel I/O via integrated Massbus controllers (RH20) for high-speed block transfers to mass storage. It incorporates an 8-level priority interrupt system and a trap facility for handling program conditions like address violations or page faults.
   • System Monitoring: Includes accounting and performance meters for timing and resource usage tracking.
   • Front-End Processor (PDP-11): Offloads tasks from the central processor, managing low-speed peripherals, console operations, diagnostics, and system startup.

3. The Hardware: Provides a detailed breakdown of the system's physical components and their interconnections.

   • Main Processor Subsystem: Comprises the EBox (instruction execution unit with various registers, arithmetic-logic units, and microcode control) and the MBox (storage controller responsible for memory management, including paging and memory buffers, and integral data channel I/O).
   • Bus Structures: Describes the various internal buses like the EBus (EBox to controllers), XBus (MBox to MOS memory), SBus (internal memory to MBox), and CBus (MBox channel logic to Massbus controllers), detailing their functions and signal lines. The PDP-11 front-end processor utilizes the Unibus.
   • Mass Storage Subsystems: Covers different types of tape control units (TX02, TU72, TU77, TU78) and disk drives (RP06, RP07, RP20), and an IBM channel adapter (DX20), emphasizing their capacities, speeds, and features.
   • Inter-processor Communication: Details how the main processor and front-end processor communicate and interact via interfaces like the DTE20, including diagnostic capabilities.

4. The Software: Explores the functionalities of the TOPS-10/20 operating system and its supported languages and utilities.

   • TOPS-10/20 Operating System: Designed for flexible, efficient management of system resources, supporting both interactive timesharing and batch processing. It features a secure and flexible file system with controlled data sharing, and a user-friendly command processor.
   • Memory Management: Utilizes virtual memory, demand paging, working sets, and balance sets to optimize memory allocation and system performance.
   • Languages: Supports a wide array of high-level programming languages including ALGOL, APL, BASIC, COBOL, FORTRAN, and the MACRO assembly language.
   • Utilities: Provides essential tools such as EDIT for file creation/modification, DDT for symbolic debugging, Dumper/Backup for data protection, SORT for data organization, RUNOFF for document preparation, and a Data Base Management System (DBMS) for complex data management. Front-end software (RSX20-F) handles console, communication, peripheral, and diagnostic tasks, offloading the main CPU.

5. Appendix A (MCA25 KL Cache/Paging Upgrade): This appendix describes enhancements for the KL10 CPU. The Cache Upgrade increases cache size and improves hit ratios, while the Paging Upgrade expands the hardware page table, makes it two-way associative, and adds a "KEEP bit" to preserve page translations during context switches, thereby improving overall system performance and reducing overhead.

In essence, the manual provides a deep dive into the architecture, capabilities, and operational aspects of the KL10-based DECsystem-10/DECSYSTEM-20, covering its hardware components, software features, and performance enhancements.