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  • Writer's picturerehsd

65816 PC Build Update (April 2022)

Updated: Apr 28, 2022

Back in January, I decided to start building a 65816 "PC." Up to that point, I had built a 6502 system with basic elements of a PC. The key elements of a 65816 PC that I would like to have:

  • Core processing (65816, ROM, RAM, Extended RAM)

  • Keyboard support

  • Mouse support

  • Graphics card

  • Sound card

  • Joystick support

  • Easy expansion

Current Hardware

As of this post, I have the hardware completed for most of the above, minus the joystick support, which is an easy add. Here's a quick run-through of the hardware so far:

Core Processing + Keyboard Support + Easy Expansion

I have completed my "motherboard" that hosts the 65816, ROM, RAM, Extended RAM, address decode logic, PS/2 keyboard input, a VIA, and ISA slots for physical connection of add-in boards (not following the ISA protocol though). Current specifications:

  • Form factor: ATX

  • CPU: 65816 at 14.16 MHz

  • Memory: 32 KB Basic RAM and 512 KB Extended RAM

  • ROM: 480 KB

  • Expansion: Seven expansion slots using ISA connectors

Mouse Support

I'm using a simple add-in card that hosts a VIA with an Arduino Mega + USB host shield. I convert the USB mouse data to simple signals that are processed on the VIA.

Graphics Card

I have developed a graphics card that supports 320x240x1B (RRRGGGBB). This card leverages dual-port SRAM for the full memory-mapped video, allowing independent writes from the 65816 and reads from the video output circuit.

Sound Card

I have developed a sound card that supports 16 channels of audio with onboard media storage (ROM + SD card). The sound card runs its own, dedicated 65816+ROM+RAM so that it can run independently from the main system 65816 (e.g., to play background music). This card evolved from the sound card I developed for my 6502 system. What is pictured in the video is the core of the sound card on a prototyping add-in card. The full sound card PCB is currently being manufactured.

Joystick Support

I plan to build a simple add-in card with a pair of serial inputs into a VIA. This will be similar to what I did on my 6502 build.

For a historical perspective, or for more details on any of my build's elements, check out my posts on these topics:

Schematics and PCB design files (EasyEDA format) are available at rehsd/PC-65816: PC based on 65816 (

Next Steps

*Lots* of 65816 assembly work! See 65816 Assembly Coding Series.


And I'm out of expansion slots... :)

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