The design of a 68030 based expandable computer

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Though the 68020 based MIDI020 computer is a workable design, it suffers from a few problems: The main one is the board is not 100% reliable. Very occasionally it will fail to start. I’ve tried to diagnose this problem but without success I can only run the processor at half the rated speed, 12.5MHz if the SIMM slot is used… Read more »

The build of a video and sound card for MIDI020

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Three PCBs arrived promptly from JLCPCB: The version 2 Test+SRAM board The version 2 Ethernet+Printer+Joystick board The version 1 Video+Sound board The version 1 of the top two boards are described at the bottom of the post about the  MIDI020 68020 computer, if you haven’t read it. The first job was to build up the version 2 Test+SRAM board. Whereupon… Read more »

The design of a video and sound card for MIDI020

For the last few weeks I’ve been working on the design of a video card for my 68020 based computer, MIDI020. Though it will principally be a video card, it makes sense to include sound generation functionality as well, and I’ve been looking at a couple of approaches to this. Though I could look at using an FM synthesis IC,… Read more »

MIDI020 build progress

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The build of MIDI020 is nearly finished. There’s been some hickups along the way, but I have managed to overcome them. My order to jlcpcb.com consisted of three boards: The MIDI020 main board The Test+SRAM expansion card The Ethernet+Printer+Joystick expansion card To make things interesting, and because I wanted to try them out, each came with a solder paste stencil…. Read more »

MAXI000 build complete and thinking about next steps

The physical construction of MAXI000 is complete: It looks good with the SIMM installed. I first attached the joystick parts. Testing the 9 pin Atari joystick went exactly as expected, as did testing the buttons on the Game port joystick I have. After writing a quick test routing for the SPI based MCP3002 (PDF) ADCs, I quickly encountered a problem… Read more »

A Pi based music player, a MISTer and a new PC

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Before getting back to work on the MAXI000 board, I thought it would be interesting to document three other little projects I’ve been working on, none of which required the picking up of a soldering iron, or writing any programmable logic. None the less they are pretty neat and were a lot of fun. I’ve been a Logitech SqueezeBox user… Read more »

A 16 bit softcore processor: Software

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I settled on CustomASM for the re-targetable assembler for my processor, after briefly playing about with the somewhat unconventional axasm. CustomASM allows you to define a processor’s instruction set in a configuration file and then assemble assembly source code using that definition. This is easiest to explain with an example. Here is the definition of the LOADI instruction: load.{width:loadtype} {dst:reg},… Read more »

A 16 bit softcore processor: Implementation

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In my previous blog post I talked about some of my goals for a simple 16 bit processor implemented in VHDL and running on an FPGA. Here is a diagram showing the top level design, as generated by the Quartus tools: For clarity the Control Unit and associated muxes are not shown; the remaining parts, plus the muxes, constitute the… Read more »