Sym-1 A 6502 Phoenix!

A simple filing system for a Sym-1 with the Resident Assembler and Editor

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Hi Hackers everywhere,
This project describes how to add a simple filing system to a Sym-1 board that has RAE installed in ROM or EPROM or EEPROM. It has several stages any of which might be of interest to either Sym-1 owners directly, or other 6502 retro computers, and possibly new hackers who are bread-boarding incredibly impressive 6502 systems. Possibly other processors might also like to build this simple filing system, may find the general principles helpful.

The project's description has been broken up onto several Hackaday pages that will be linked back to this page as a summary source. Check the Log of associated pages below. While not complete yet, you may find some interesting, even entertaining reading, good luck!!

(Editorial Note: The etherial glow at the top of this page is a germicidal UV lamp that I have been erasing EPROMs with for the last 50 years. The sharp eyed will note the EPROM just underneath. Ahh the smell of fresh Ozone, real computing!!!).

Retro computing is a good reminder of how far things have improved, but to go back there? I have yet to own any computer that I have felt that I have exhausted all possibilities to learn and interact with. My work as a teacher for 36 years usually mandated that we move the children to the next stage of technology to keep the students as up to date as possible. This inevitably meant that quite capable designs were declared "old fashioned" well before "all that they offered" was explored. I am returning here to my second SBC I purchased around 1980, the Sym-1 by Synertek. Not to turn the world around but just for me to savour again the thrill of working with a great design that promised so much, and sadly as I found not enough time to explore. However there maybe other gems that other people can glean from these activities, so here we go...

I sold my original Sym-1 around 1984 to buy an Acorn BBC-32Kb. So I bought another Sym-1 around 2017 and this time wanted to use the RAE, the Resident Assembler and Editor, as the main software on it. I had always enjoyed Assembly Language and was yearning to not do it by hand this time, but to use an assembler. The rise of the Arduino systems had drawn me back to bits and bytes, and made me remember just what these retro machines also offered.

To this end I first had to get the Sym-1 to a convenient level of operation. Being familiar with its versatile design, I set about exploring what could be done. Here is a simple list of the progression of the project.

1. Power Supply: 5V LED supply (done)

2. Expand the onboard RAM (done)

3. EPROM Programmer (done)

4. Expand RAM off the board to 32k or more (done)

5. Soft load major ROM images (done)

6. Use 2764 (8kx8b) EPROMS (done)

7. SD Card storage and retrieval. (done)

These stages will be explained and outlined in separate Hackaday Project Logs (below), as not all parts will interest everybody, and this will make the story a bit more modular. The files developed are linked to this page as I can't see how to link then to the relevant Hackaday Pages. This will also provide a short cut for those who don't need all my explanations of what needs to be done.

Given the number of new designs for retro 6502 systems (especially those amazing breadboard constructions) they could do well to try to incorporate the RAE as their main language support. It provides very open ended programming capability, and given the Arduino IDE today, well ahead of its time. I am not sure what would be required to get the Sym-1 monitor and RAE to transfer to a Bread Board Build for a 6502, but I hope that my work will show at least a filing system is well within easy reach.


Use this program to Burn an 8Kb EPROM 2764 with little more than a Mega2560, SD card reader, a 5-12V buck converter. Read ROMs and EPROMs and burn EPROMs.

ino - 32.98 kB - 12/06/2023 at 10:05



An Arduino Mega 2560 program to provide the MFS 2.3 filing system on the SD card to the Sym-1. This is very rough and ready but does the job. Not much is optimised or generalised but it does work!

ino - 21.85 kB - 03/05/2022 at 06:46



The binary file of the MFS 2.3, which loads at $9000

x-extension-bin - 1.37 kB - 03/05/2022 at 06:42



The assembler details for the MFS2.3 image to be loaded at $9000, use Mass Werk to compile it. A fantastic software effort.

asm - 20.06 kB - 03/05/2022 at 06:39



This is paper tape version of the MegaFilingSystem 2.3 to be loaded at $9000, and compatible with RAE and providing monitor saving and loading extensions. Use it with .LP If less than 4kB they can be loaded at 2400Baud using GTKTerm (if they are too big they will stall).

ptape - 3.87 kB - 03/05/2022 at 06:37


View all 11 files

  • 1 × Sym-1 SBC Synertek c: 1976 A 6502 prototyping system
  • 1 × Arduino Mega 2560
  • 1 × Arduino WiFi and SD Card interface Adafruit CC3000 WiFi shield V 1
  • 1 × Hook Up wires Cut up solderless breadboard connectors to solder to Sym-1 plug, and pins for Mega
  • 3 × 44 Pin Socket 805-44P 3.96mm pitch 22 by 2 double sided socket

View all 10 components

View project log

  • 1
    Please consult Project Logs (above) for various aspects of this build/project

    How to upgrade the monitor functions and add a filing system to a retro 8 bit computer, the Sym-1, using a Mega2650+SD card

View all instructions

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michael.cvet wrote 01/28/2024 at 11:53 point


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