The Processor Technology SOL-20, introduced in 1976, is an 8080-based S-100 bus microcomputer system that has many interesting design features. Unlike most other micros of its time, the SOL-20 has an integrated terminal complete with keyboard and composite video output. The display circuitry, which is integrated onto the system board, has 1k of RAM that is mapped into the system's address space. Writing characters to the display can therefore be accomplished by directly writing to the video RAM.
The SOL-20 has a removable ROM board called a Personality Module that can contain monitor or bootstrap firmware, allowing the system to be functional at power-on without manual entry of bootstrap code. A cassette tape interface, a serial port, and a parallel port are integrated on the system board, and 5 S-100 slots are available for adding memory and other options.
The SOL-20 uses a Keytronics capacitive keyboard. With age, these keyboards tend to fail due to deterioration of the foam pieces that connect the dielectric/plate pads to the plastic keyswitch mechanisms. Failed SOL-20 keyboards can be restored to operation by replacing these foam pads, which can be obtained from cannibalized Keytronics PC-clone keyboards or from Jim Willing of Jim's Computer Garage.
Home | Information | Machines | Projects | Documentation | Links