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1980s Computers Explanation of terms

The Sol-20



Processor Technology Corporation (US)


(Named after Les Solomon, the editor of Popular Electronics, which published articles on the Sol-20. There was also the Sol-10 which lacked the numeric keypad and expansion slots.)

Date Launched

Late 1976


$1649 as a kit or $2129 ready assembled, for the 'System II' which included 8 KB of RAM, a TV monitor and a cassette recorder.
(Not sold in UK)

Microprocessor type

Intel 8080 @ 2 MHz

ROM size

1 kilobyte

Standard RAM

Minimum 1 kilobyte.
At least 8 KB was fitted in most systems, plus 1 KB of video RAM.

Maximum RAM

64 kilobytes total RAM + ROM + PROM.

Keyboard type

Typewriter style with numeric pad

Supplied language

None built-in but BASIC-5 was supplied on tape.

Text resolution

64 x 16 characters

Graphics resolution


Colours available


Example Screenshot

Sol-20 screen
A 'shooting' game using the Sol-20's text-only display, which had a high resolution for 1976.



Cassette load speed

1200 baud
Disk drives could be attached to the S-100 bus, or a paper tape reader could be connected.

Dimensions (mm)
Weight (grams)

Not known
Not known

Special features

The first self-contained desktop computer, with an integral keyboard and video display adaptor (suitable for modified TV, or video monitor), plus serial and parallel interfaces, as standard.
The case was well made, of sheet metal with solid walnut side panels.

Good points

Could be expanded via the five internal S-100 slots.
An early wordprocessor, called Electric Pencil, was written for the Sol-20.

Bad points

By the standards of 1976 the Sol-20 had few faults. Perhaps the main one was that because of the way the ROM and display were memory mapped, it could not have more than 48 KB of contiguous RAM and thus could not run most CP/M programs (which needed 64 KB of RAM.)

How successful?

Around 10,000 were sold, a relatively large number for an early desktop computer.
Processor Technology closed in May 1979.


The Sol-20 was mostly designed by Lee Felsenstein, who also designed the Osborne 1, and partly by Robert Marsh, one of the founders of Processor Technology, and Gordon French.
It was originally described as an intelligent computer terminal for interfacing with mini-computers via an RS-232C link.

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