This repository contains the hardware design for a heavily revised Dragon 32 computer main board. Unlike my other designs this does not conform to the original footprint and port placement.
The design is most definitely experimental and absolutely unproven
The board differs from standard with the following features:
- 1MB SRAM - 64k address space, 32k pages (lower and upper ram space) - theoretical 16MB limit
- Multiple (selectable) cartridge slots
- 2 button joystick ports (compatible with original single button joysticks)
- Hardware serial port (as with Dragon 64)
- Switchable ROM banks (as with Dragon 64)
- Twin AY-sound generators (6 channels)
- SAM X4
- Advanced, addressable 6847 compatible VDG (one of different video output options)
- Fast CPU options (1.8 or 3.6 MHz)
- ISA style connection slots for further expansion (paged 4MB assigned to each)
The regular interface ports are kept to the left hand side of the board although the serial port is a more commonly accepted DE9 configuration instead of the 7-pin DIN
The rear of the board is dedicated to the cartridge slots. The power and video output is on the right of the board.
The board itself should (just) fit inside a regular Dragon case but the power and video interface needs to be external. The mounting points are all wrong but it should fit.
The design is intended to fit within an ATX case and conforms to the smallest ATX standard so almost any ATX case should suffice with a single caveat - the cartridge ports may overlap the space given over to the power supply, especially on older designs. A modern case design that places the power supply away from the board (typically the bottom of the case) should have no problems.
The keyboard connector is compatible with the original Dragon design but also includes an extra +5V which makes it very convenient to fit an adapter for other styles of keyboard using a microcontroller.
The design integrates most of the designs and upgrades I've developed for the Dragon, all into a single board which helps to reduce the footprint and power requirements
At this point the task is to play around with the component layout to find a relatively simple and efficient approach. The board size, port positions and component layout has not been fixed. The only exception to this is the three video connectors - these can be moved around the board but must retain the same relative positions
Details on the design of the board and operational logic is presented in the project WIKI
The project needs review and ultimately, testing, once the design progresses that far.
If you want to help please get in touch first to keep the work flow consistent and to avoid potentially disasterous conflicts
Currently the project needs review of the schematics prior to build, and a rewrite of the samX4 VHDL and GAL16V8 logic that drives the cartridge ports
See the project page for details of each outstanding task: Dragon RevX4 Plus Project Page