Processor Technology SOL-20

Processor Technology was started as an add-in card company producing mainly memory cards for the MITS Altair 8800. Like many similar companies, they quickly expanded into producing competing systems themselves.

The SOL-20, designed by Lee Felsenstein and conceptualized by Bob Marsh and Les Solomon, was a seminal personal computer that was first to include integrated keyboard, video and ROM in the same package. This model quickly became the industry standard for user friendly personal computers.

The Sol-20 was an 8080 based system that incorporated the Processor Technology VDM-1 to produce video on a television or composite monitor. The system included a monitor ROM that allowed the user to boot the machine into a semi-usable mode on power up.

The machine in my collection is in exceptionally good condition and works perfectly.

The SOL-20 had a very clean design with a large motherboard, a five slot S-100 card cage and a relatively small power supply.

From the back you can get a clear shot of the card cage and the "personality module" on the bottom right.

The SOL-20 runs perfectly and a quick memory dump can be seen here on a standard composite monitor hooked up to the system.

I've got a manual around here somewhere. As soon as I dig it up I'll post pictures.

(Submitted February 27, 2008 14:06:56 by Howard Dimmick)

I built one of these from a kit in 1978

(Submitted April 13, 2007 14:19:11 by Rick)

My goodness, a Sol-20. Sure brings back memories. I remember reverse engineering the TARG game so I could make more things drop faster from the sky (run up a high score). In 1977-1978 I wrote a 4k chess program in 8080. I never commercialized the program, but it beat Boris (early 80's chess playing computer). My obsession with my Sol-20 inspired my switch to software engineering (I was a designer/programmer -- video games and R&D -- for 30 years) from teacher of Mathematics.

(Submitted March 31, 2007 05:44:41 by Jeff Smith)

In 1975 I saw an article in an issue of Popular Electronics about the sol-20. A computer, in kit form too! Move over Heathkit. The soldering and such went pretty smoothly but we missed an solder joint.Just one.Out of about 2000 of them.Finally it jumped out at us. And when the rosin cloud drifted away we plugged her in again and a cursor was born.

(Submitted January 30, 2007 21:23:16 by Gary Bisaga)

Man, I learned how to program in assembly language from the Sol-20. I built mine (with my dad's help) when I was 15. I used to lay on my bed and pore over the assembly language listing of the Personality Module for hours and hours - and I still remember some of the comments in that listing. Man, what a waste of good brain cells. :-)

(Submitted November 29, 2006 06:01:53 by Bob C. Hookham)

I built the SOL-20 as a school project in 1976- 77, as an alternative to the time-share computor that our high school was renting. I was the Lead tech (17 yrs old) of the three of us who built it. The net result was that our high school was so impressed with it, that the following school year they bought 15 of the new Apples the were being marketed at that time. Within 3 yrs, I was told that my HS had purchased over 200 computers for student use, in a HS of only 1200 students. Our electronics program in the '70's and early '80's was so far ahead of the local Jr college, that students who were taught under a specific instructor were given FULL credit towards their EE Degree. Thanks for the pictures, they bring back a lot of memories (a GOOD thing). BCH

(Submitted May 31, 2005 17:41:35 by Mac Goodell)

Your SOL-20 looks great. I have one stored in my garage. My students and I raised the funds, and assembled the kit for a long time, and it worked great. We used a regular TV set (20 inch) for demostrations. How frightened most people were when we ran Eliza and analyzed peoples' psyches.I used the machine to teach Basic programming, and some students wrote and sold game programs to software venders. It would be a celebration whenever we discovered another $250, and bought a kit to make another 64K memory card! If anyone ever expresses interest in the SOL-20, for a museum display, you could have them contact me at m-and- m@softcom.net.

(Submitted April 15, 2005 16:14:14 by Larry)

The SO-239 connector is composite video output for the monitor.

(Submitted April 4, 2005 18:36:46 by Tandy)

I wonder what the SO-239 connector is for? Looking at all these old computers kinda makes me appreciate PCI and Plug n Play. :-)

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Description
Manufacturer	Processor Technology
Model	Sol-20 Terminal Computer
Date Announced	1976
Date Canceled	Unknown
Number Produced	About tens thousand
Country of Origin	USA
Price	$1,000 kit, $2,000 assembled
Current Value	$250 and up

Specifications
Processor	Intel 8080
Speed	2 MHz
RAM	Usually 8K-64K
ROM	1 or 2K ROM, 1K video
Storage	Cassette tape, 5.25" and 8" disk
Expansion	5 expansion slots
Bus	S-100
Video	64x16 black and white text
I/O	Parallel, Serial
OS Options	CP/M, BASIC, NorthStar DOS and a variety of others

Notes	The SOL-20 was probably the first PC to incorprate a keyboard and video with the machine. This form factor obviously became the norm when the Apple ][ debuted a year or more later. The SOL also included ROM "personality modules" that allowed the computer to have some native code at power on. Other than that, however, the SOL-20 was a fairly typical S-100 system in a different package.

Related Items in Collection	MITS Altair 8800, IMSAI 8080 and a variety of other S-100 systems.
Related Items Wanted	Helios disk subsystem, additional personality modules, additional software, expansion chassis, etc.