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X65 Project

X65

Modern 8-bit Computer

READY
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X65 is an 8-bit microcomputer for the modern era.
It blends the core principles of 8-bit computing with modern hardware components, making it practical and capable of handling everyday tasks.

Components

• CPU: WDC 65C816 @ [~4MHz][17]
• RAM: 16MB PSRAM (flat, no banking)
• Video: CGIA (custom VPU chip)
  • Output: DVI-D, 384×240px @480p
  • 256-color [palette][18]
  • 4 graphics/sprite planes:
    • Background graphics Display List
      (ANTIC-style)
    • 6 graphics modes
      (C64-style + HAM + MODE7)
    • Hardware scrolling
    • 8 sprites (per plane), up to 64px wide;
      built-in multiplexing
  • Three types of programmable raster interrupts
• Audio:
  • Yamaha SD-1 YMF825 (FM synth, OPL3-class)
  • 2× sample playback channels
  • stereo sampling ADC
  • 2× RCA out, 2× RCA in, 2+1 Exp-in
    via ROHM BD34602FS-M audio mixer
• I/O:
  • RP816-RIA: USB mass storage, HID
  • ESP32-C3: Wi-Fi, Bluetooth, USB-UART
• Ports & Expansion:
  • 6× USB ports + 2× internal USB headers
  • 2× DE-9 Joystick / GPIO (via TI TCA6416A)
  • Expansion: CPU bus, 4× IO_EN, 4× IRQ, Audio-In (mixed), I²C
• Interrupt controller: memory-mapped flags register

Current [Milestone 1 prototype][19] is available as a DEV-board for developers to experiment with.
Final hardware is going to be an all-in-one keyboard computer form factor.

OS/816

X65 runs its own native operating system: OS/816.

OS/816 is built specifically for the 65C816 and leverages its capabilities.
It provides:

• Simple multitasking environment
• Application framework
• Shell access
• Virtual screens
• Low-level programming interfaces

All without legacy overhead or unnecessary complexity.

The system is designed to be practical and transparent. You can write code close to the hardware or build higher-level tools as needed. It is easy to follow, easy to extend, and won't get in your way.

Why X65?

We need "Understandable Computers" to make computers understandable.

Simple machines with clear component purposes make the best teaching tools - not just for learning, but for growth. They invite curiosity, exploration, and insight in ways modern systems no longer do.

The X65 is also just fun.
It is a machine you can truly get to know, shape, and expand.
With much of its hardware defined in software, it is uniquely easy to modify and make your own. In an age of sealed boxes and hidden layers, X65 brings back the sense of agency we once had - the joy of a computer that answers to you.

[17]: {% post_url 2024-03-07-VAB-memory-optimization %} [18]: /media/2024-06-08_colors.html [19]: https://github.com/X65/schematic/blob/main/protoC/protoC.pdf

Contact

Join 💬 Discord Community,
Email 📨 [email protected]
Call 🖀 X65.zone BBS.