Links

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.

• Michael Gardi has written a Sol-20 emulator, written in Python & the pygame library. It is part of a larger project to build a full-scale Sol-20 reproduction computer. Very impressive!
• Here is a great video from youtuber "myapple1976" of their restored and fully functioning Sol-20 computer with Helios II disk system. The video is a run-through of the sales demo disk from 1977. Fantastic stuff.
• Bitsavers has a folder hierarchy containing manuals and brochures from Processor Technology. It is well worth the visit.
• Dave from osiweb.org has designed a number of replacement parts for Sol-20 computers. First, a complete replacement keyboard for the Sol-20 using modern Cherry keyswitches. The design is open source. There are two versions of the keyboard encoder: DIP only and surface mount. He has also design replacement wood sides, consisting of design files and guidelines on construction. Finally, he has designed a replacement personality module that can contain multiple PM images, with the active one selected by jumpers. It also permits remapping of the RAM/ROM from Cxxx to Fxxx to increase available RAM.
• Julie Porter has done an amazing project (github repository), namely transliterating Extended Cassette BASIC from 8080 asm to AVR asm. Although the cassette I/O operations are stubbed out, the rest of it works. As a bonus, Julie tells the tale of her own background and Processor Tech's part in it.
• Mike Douglas over at deramp.com has been hard at work writing new Sol utilities and building up a useful site in support of a few different computers, including the Sol-20. He has utilities for transferring disk images between a Sol-20 and a PC, and a CP/M loader which allows playing Sol-20 games originally targeted for use with the SOLOS ROM. Mike has also put up a mirror of this site, in case this one ever disappears. Thanks, Mike!
• Howard Harte has a quite a nice collection of manuals, including a section on Processor Technology products. Many of the docs there overlap those from this website, but there are also many that did not, so go have a look.
• The tireless Dave Dunfield has a collection of useful S-100 documents, including a section on Processor Technology cards.
• Lee Felsenstein, the designer of the VDM-1 and much of the Sol-20, has his own website, while this website has an audio interview with him.
• Dr. Hugo Holden has a website full of interesting work he has done designing, reverse engineering, and repairing various electronic items. Every project is accompanied by a fantastic write up. Two recent projects he completed were an investigation of the Sol-20 cassette interface and solving a Sol-20 lockup problem.
• Hak5 has a nice interview with Lee Felsenstein at MakerFaire 2013.
• Santo Nucifora has a Sol-PC, which essentially was a standalone Sol-20 motherboard sold by Processor Technology. They didn't sell well, as most opted to get the Sol-20 configuration. Santo has done a great job with his presentation. This one was configured into a case with a linear power supply, but it looks nothing like the Sol-20. He also has restored a Helios II dual disk drive back to operating condition.
• Rich Cini has a collection of documents he has scanned, including some Processor Tech docs
• Herbert R Johnson has many S-100 related documents he is willing to copy and sell for a nominal fee. He even has a page of Sol documents available.
• Bill Sudbrink has a neat utility, RUNENT that allows running .ENT format files from the CP/M command line.
• Martin Ward has written a sophisticated KCS/CUTS tape decoder, in Perl. Although it can be rather slow, due to the nature of Perl, it has worked well for me, given a reasonable recording and the right parameters.
• Although I have my own page on how to repair the Sol keyboard, I've come across two sites that work around that by making their own pads! Geoff Harrison has a nice Sol-specific write up. Here is another technique for the Apple Lisa keyboard, which also appears to be a Keytronic design.
• Here is something quite interesting and unusual: an old article about micro computers, the Sol-20 specifically, written by a noted writer. Check out the article Living With a Computer by James Fallows from the July, 1982 Atlantic Monthly.
• Here is a ebay sales pitch for a nicely restored Sol. It was produced by Mike Davis, who has created some interesting and useful products for the Sol.
• The Digibarn Computer Museum has an enviable number of interesting computers and an even more interesting and enviable place to keep them. Of special note, it has an informative Sol page with a number of photos and links to other Sol information. Be sure to check out the panel of key Processor Technology employees who gathered together for a 30th anniversary celebration at VCF 9.
• The Atari Archives has been doing a fantastic job of getting permission to scan and post a lot of classic computer publications. One of them is The Best of Creative Computing, Volume 3, where there is a review of the Sol-20.
• Retroarchive.org has a lot of great information about old computers, but the one that is probably most of interest is the folder containing all the CPMUG (CP/M User Group) disk images. These aren't necessarily Sol-specific, but are still highly relevant.
• oldcomputers.net has a nice write-up on the sol.
• Corestack has a picture of a Sol opened up. You can see the personality module with the four eproms in the upper left corner of the picture. It also has a very interesting, but brief, description of another machine designed by Lee Felsenstein, the Micro-Expander. Lee also designed the what is undoubtedly his most famous machine, the Osborne microcomputer.
• Speaking of the Micro-Expander, Florian Stassan has done a great job documenting his restoration of a Micro-Expander.
• David Williams' Trailing Edge site has a Sol computer that I have a special connection to. I gave him the Sol and he gave me an Exidy Sorcerer.
• Randy Wilson has HTML-ized some Sol literature for our amusement
• Charles Eicher restored a Sol-20 back to operation. A while later he gave an update on his progress. Charles also has a picture of his Sol generating some blocky graphics via the Graphic-Add display mod.
• It may be an obvious source, but Wikipedia has an entry on the Sol-20.
• The Computer Closet has a web page and has a couple scans of ads
• Stan Veit wrote an interesting book on the early history of the micro-revolution, written as an insider. There is an entire chapter on Processor Technology and the Sol computer. Pick it up for only $5.
• Erik Klein has a Sol-20 page, with a number of commenters.
• Where does the Sol fit in the timeline of microcomputers? Here's one version.
• The PC-History website has a page on the Sol along with some contextual historical information.
• Stan Sieler has some information on the Sol-20.

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.

• The Old Computer Museum
• The Computer Museum of America
• The Old Computer Hut

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

AND NOTHING ELSE.

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.