The first section of links are ones that have original content of some kind. Nearly all of these links are to external websites, so it is to be expected that some will go dark once in awhile.

The following are pages about the Sol-20, but have less information, typically a photo of their machine and some basic details about it, like original price, CPU type and speed, and amount of RAM. Some of them contain just a little bit of information on the Sol but have interesting information about other old machines, so it might still be worth a visit.

This section is a bit different in that it is an ad. Although this website has no ads, I'm making an exception for Martin Eberhard because he is obviously not doing this to make money but to help support the community. Martin has created an EPROM programmer for the MM5204 EPROM, a kind commonly used with Sol-20 computers and other hardware of the same era. Here is Martin's summary of the device.

New MM5204Q EPROM Programmer Kit

If you are restoring a Processor Technology Sol-20, then you have probably come across these early EPROMs from National Semiconductor, the MM5204, the MM5204Q and the military-grade MM4204Q. These were used on the early versions of the Personality Module.

Wouldn't it be great if you could read, program, edit, and copy these early EPROMs? Are you frustrated that all of the so-called 'universal' programmers can't program these EPROMs? So was I... So I designed the ME5204 - a full-featured programmer for the MM5204 EPROM.

I built a small run of ME5204 PC boards for myself and a few friends. I am offering the last PC boards as kits for $55 each, plus shipping. (This is about what it costs me for materials.)

The kit includes the following items: 1) The bare printed circuit board, 2) a bound, detailed, 77-page manual, 3) the PIC microcontroller, programmed with the ME5204 firmware, 4) A DVD with documentation, including my PIC firmware source code, the MM5204 spec, and component specifications for most of the parts used on the board.

The ME5204 EPROM programmer connects to your computer via RS232 at 9600 baud, and requires only a simple terminal program, like Hyperterm. It allows you to blank-check, read, edit, copy, program, verify, and checksum MM5204, MM5204Q and MM4204Q EPROMs. You can transfer files to and from the ME5204 in either Intel Hex format or Motorola S-record format. All commands are explained in the manual, and also in detailed help screens. The ME5204 works around the world, supporting 110-120V 50/60Hz, as well as 220-240V 50/60 Hz.

The manual is illustrated, extensive, and thorough. It includes assembly instructions, debug and bring-up instructions, operating instructions, theory of operation with timing diagrams, schematics, a complete bill of materials with Digikey or Allied Electronics part numbers and prices for every single component used, and templates for drilling the chassis holes. I've even included a copy of the MM5204 spec.

The firmware includes a built-in Loader, that allows you to upgrade the firmware in the future via the serial port, without any special hardware (such as the Microchip PICkit 3).

The total cost for all of the components that you will need to buy from Digikey and Allied Electronics (as of a month ago, when I bought my components) comes to about $75 plus shipping. If you buy some of the parts on eBay, it will cost you a bit less.

To build this kit, you'll spend a few hours with your soldering iron. When you are done, you can read old MM5204-family EPROMs, and save their contents as hex files on your computer. You can program MM5204-family EPROMs with files you've downloaded from the Internet, or with your own code, directly from the output of your assembler. You can read an EPROM, edit its contents if you like, and write the edited contents back to another EPROM. It works great, and it's fun to build.

This programmer is based on the design of my previous programmer, the ME1702/A. You can read comments by ME1702/A customers online - google "yahoo altair me1702A"

To be clear, what I am selling for $55.00 (plus shipping) is:

  1. The bare ME5204 printed circuit board
  2. the 77 page manual
  3. the PIC microcontroller, programmed with the ME5204 firmware
  4. the documentation DVD


Martin also has made a faithful replica of the MUSIC system board, which allows a Sol (and potentially any S-100 computer) create polyphonic music. You can see an example of it at the website of Mike Douglas. If you are interested, there is contact information at the bottom of the page concerning getting one.

If you are interested, please contact me and I'll connect you with Martin.