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There is a blog for this project at and an emscripten version which is identical to the hardware version at

Eris is an open source 16 bit retrocomputer design which can be built cheaply and easily and has low implementation requirements. It can be built for about £10 or so + cost of preferred keyboard.

It's a virtual machine system, so the code that runs on it is written in its own assembler, so porting is much more reliable.

Currently it runs on SDL , on Linux, Windows, Javascript via emScripten and Raspbian.

It runs stand alone on a ESP32 chip with FABGL compatible hardware (a few discrete components) or the TTGO VGA32 board or compatible - this is the reference design.

Future platforms : PiZero, definitely. Possibly others.

This is stuff that actually works now. Not planned, theorised, possibilities.

It is Beta at the time of writing, but bugs have been minor. I'm writing a pile of games for Retrochallenge April 2020 and the real purpose is to dogfood test it. Though this is cross development , but I'm pretty sure the editor works pretty well. I soak tested SPIFFS (the ESP32 storage system).


  • 16 bit 100% orthogonal RISC-style CPU running at slightly under 1 MIPS on ESP32. (it has bits of IMP-16, bits of ARM RISC and bits of CDP1600)
  • 24k RAM and 16k ROM 16 bit words, max 47.75k RAM words
  • 320x240 4 bit colour display driven by a baby blitter, does not use Program RAM.
  • 2 tone and 1 noise channels.
  • Running on ESP32, Javascript , Raspian and Windows/Linux emulator (only uses SDL)
  • Uses system storage - Local HD, SPIFFS and SDCard dependent on platform.
  • Files can be downloaded from the internet into the platform
  • Files can be uploaded from the platfom for backup

System Software

  • python3 Cross Assembler, Sprite Generator, Basic tokeniser for cross development.


  • 53 x 30 text display
  • Commodore style screen editor which works like a text editor
  • Line, Rectangle, Ellipse Graphics Text functions.
  • Single colour sprite system supporting 24 at once.
  • Standard joystick interface (it maps onto arrow, shift and ctrl)
  • Background sound generation
  • Redefinable function keys
  • Keyboard internationalisation

Integer Basic

  • Integer and String, one and two dimension array types
  • Approx 12-13 times quicker than C64 Basic (to be fair, this uses floats)
  • For, While, If/Else/Endif or If/Then, Repeat structures
  • Long variable names
  • Named procedures and value parameters
  • Local variables
  • Commands for sound, sprites, joystick, keypress, graphics etc.
  • Indirection operator (like BBC Basic or BCPL)
  • Inline Assembler (like BBC Basic)
  • Built in quasi-Forth programming language (which is much easier than assembler but less efficient)
  • Has GOTO, GOSUB and RETURN but you don't need line numbers except editing.
  • Listing Indents structures and does syntax colouring.
  • Message internationalisation (could internationalise keywords ...)
  • Hidden lines for support code ; you can't edit or list any line no > 32767 or 0 (the point of this is that learning materials can hide support routines)


  • Hardware Description
  • Basic Reference


Eris is an open source 16 bit retrocomputer design which can be built cheaply and easily







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