Disclaimer fun: Electronics is just a hobby of mine and I dont claim to be an expert at anything. Nothing has been extensively bug tested and there's no guarantees, warranties, claims of suitability etc. Information and code is provided (largely uncommented) for research only, but please credit me if you find it useful - thanks.

Ubicom SX28 Microcontroller Source Code:

Sprite controller
Sound system
Graphics controller

Microchip PIC PIC16F627 Microcontrolller Source Code

PS/2 keyboard controller
Serial interface

CPLD Schematics: (Xilinx ISE 7.1 format schematic files - zips include .png bitmap versions)

Z80 Main interface
IDE interface
Graphics controller 1
Graphics controller 2
Graphics controller 3

Z80 Source Code:

Operating System and BIOS
Protracker replay routine (note: has "incomplete" FX handling, go here for newer Z80 tracker
Boing Demo (archive includes protracker code)

Documentation etc:

Hardware reference info IE: RAM layout, ports, registers etc - Doc file