Part 1: The X65 Microcomputer

This section covers the hardware and design philosophy behind the X65, detailing what makes it unique and how it builds upon the legacy of classic computing. Topics include:

• Chapter 1: Introduction
  • The Vision Behind the X65
  • Why the 65816?
  • Design Philosophy: Retro Aesthetics with Modern Usability
  • Who Is This Computer For?
  • What This Book Covers
  • Looking Ahead
• Chapter 2: System Architecture Overview
  • CPU: The 65C816 in Native Mode
  • Memory Map and Addressing
  • Interrupt Handling and Priority System
  • System Clock and Performance
    • CPU Bus Circuitry
    • VAB Memory Cycle Optimization
• Chapter 3: Memory and Storage
  • RAM Layout: Flat 16MB Address Space
  • Direct Page Usage (No Zero Page!)
  • Memory-Mapped I/O (MMIO)
  • Persistent Storage (If Any, e.g., Flash, SD Card, LittleFS)
• Chapter 4: Graphics and Display
  • The Color Graphics Interface Adaptor (CGIA)
    • Principles of Operation
      • Background Graphics Plane Operation
      • Sprite Plane Operation
    • Real-Time, Non-Persistent Raster Line Rendering
    • Display List and Scan Pointers
    • Graphics Modes, Planes, and Color Palette
    • Beam-Chasing for Efficient Rendering
    • Raster Interrupts and Mid-Frame Changes
    • Sprite Multiplexing System
    • Sprite Dimensions and Features
    • Additional Sprite Features
    • Memory Banking for Graphics Rendering
    • Advanced Graphics Modes
    • Summary
• Chapter 5: Sound and Audio
  • Yamaha SD-1 (YMF825) FM Synthesizer
    • Features of the SD-1 FM Synthesizer
    • Integration with the X65
    • Mono Output and Mixing
  • Dual PWM Audio Channels
    • Key Features of the PWM Audio System
    • How PWM Works in the X65
    • Applications of PWM Audio
  • Integrated Mixer
    • Mixer Capabilities
    • Summary
• Chapter 6: Input and Output Interfaces
  • UART and Serial Communication
  • RP816-RIA: USB Mass Storage and HID Support
  • ESP32-C3: Wi-Fi, Bluetooth, and USB-UART
  • DE-9 Joystick Ports (Retro Gaming Interface) and GPIO
  • Expansion Port: Full CPU Bus, Audio-In, and I²C
• Chapter 7: Development and Emulation
  • X65 Emulator: Features and Capabilities
  • Web-Based Emulator Access
  • Integration with Development Tools

Key Topics Covered

• The vision and goals behind the X65 project

• The 65C816 CPU, its advantages, and how it operates in native mode from boot-up

• The memory model, including flat 16MB addressing and efficient direct page handling

• The graphics system, which uses a beam-chased display list instead of a framebuffer

• The sound system, leveraging a Yamaha SD-1 FM synthesizer for rich audio

• Peripheral support, expansion options, and system input/output design

By the end of Part 1, readers will have a complete understanding of the X65’s architecture and what makes it a powerful yet accessible computing platform.

What to Expect Next

In the following chapters, we will dive into the technical architecture of the X65, exploring how its components interact and how it provides a unique platform for low-level programming and hardware experimentation.