In January of this year, I decided to try to build a new system based on the 65816 processor. It has now been almost five months, and I thought I would share the current state of the system.

65816 PC Build Update (April 2022)

While it's not "done," and likely never will be, it has come a long way. I have been learning a great deal through this project!

The primary components of the system include:

• 65816 motherboard

• USB mouse add-in card

• Video add-in card

• Sound add-in card

• Joystick / controller add-in card

65816 Motherboard

• ATX form factor

• W65C816S6TPG-14 processor, running at 14.16 MHz

• 32 KB basic RAM

• 480 KB flash ROM

• 512 KB extended RAM

• PS/2 keyboard

• Onboard SPI support

• Seven expansion slots (using ISA connectors but not using ISA protocol)

• 480x320 debug screen

• Address decode logic with programmable logic device (PLD).

• More details

USB Mouse Add-in Card

• Arduino Mega 2560 with USB host shield

• Interrupt-based

• USB data sent to system through an onboard W65C22S6TPC-14 versatile interface adapter (VIA)

• More details

Video Add-in Card

• 320x240 resolution, with one byte per pixel for color (RRRGGGBB)

• Card drives sync with a pair of PLDs.

• Daughter cards for video memory. 128 KB of dual-port static RAM (expandable to 256 KB).

• Output does not require system processor usage. System and video card can both access video memory simultaneously.

• More details

Sound Add-in Card

• 18 channels / voices

• Dedicated audio coprocessor (65816) running at 10 MHz

• 32 KB basic RAM (28 KB usable due to addressing design -- DPRAM and I/O using the 4 KB)

• 512 KB firmware flash ROM

• Onboard 512 KB flash ROM for media assets

• Onboard 64 GB SD Card for media assets (uses onboard SPI for communication)

• Dual-port static RAM for communication from/to the host system

• Leverages three VIAs and six programmable sound generators

• Playback independent of host system

• Supports interrupts from system for commands and data

• Can raise interrupts back to system

• Two-line debug screen

• More details

Joystick / NES Controller Add-in Card (and Add-on Board)

• One ATARI joystick port

• One NES controller port

• Supports both interrupts and polling

• More details

Overall System

• System to USB mouse communication handled through VIA and Arduino Mega 2560

• System to video card communication handled through dual-port SRAM.

• System to sound card communication handled through dual-port SRAM and interrupts.

• System to joystick/controller communication handled through VIA and optionally interrupts.

• The entire system is running well at full speed (14.16 MHz for my build).

• I am supplying 5.10 V to the system. Current draw is 1.37 A. The system debug screen and associated Arduino Mega 2560 are currently powered off of USB from my PC.

• Along the way, I have so far developed several supporting utilities (mostly Winforms), including graphic import and conversion, PSG controller, music editor, MusicXML importer, a 65816 emulator, and a sound card emulator.

• I have months of assembly work ahead of me.

I have posts on many different aspects of the above, including links to schematics and code. See BLOG | rehsd (rehsdonline.com).

Questions, suggestions? Drop me a line! Thanks!

Some related posts:

• VIA Timer for Background Tasks, an NES Controller, and a Debug Screen (rehsdonline.com)

• 65816 - Cached sprites, a joystick, and Mario enters the scene. (rehsdonline.com)

• 65816 Sound Card Substantially Complete! (rehsdonline.com)

• Creating New Music for My 65816 Sound Card (rehsdonline.com)

• 65816 Motherboard - Building Your Own (rehsdonline.com)

• Sound Card 2.0 PCB Build (rehsdonline.com)

• 65816 Assembly Coding Series (rehsdonline.com)

• 65816 PC Build - Lessons Learned (running post) (rehsdonline.com)