8-bit microcomputer built from commercially available and home-built components
This project is a personal journey back in time to the heroic age of computing: a newly built, classic 8-bit system, in which I supplement the factory components with modules of my own design. My goal is to revive the joy of discovery, while on this new machine, legendary languagessuch as BASIC, Fortran or Cobol come to life again.
| components | type, size, etc. |
|---|---|
| motherboard | SC126 (Stephen C. Cousins) |
| firmware | RomWBW SCZ180_sc126 v3.5.1 2025-05-21 |
| processor | Z180 processor (33 MHz - at 18.432 MHz) |
| ROM | 2 x 512 kB byte Flash memory |
| RAM | 1 x 512 kB byte RAM |
| bus | RC2014, 9 BP80 socket |
| disks | 32 MB CF card |
| SD card | |
| connectors | 2 x serial RS-232 |
| 2 x serial RS-232 TTL | |
| 2 x paralel TTL | |
| 1 x CTC TTL | |
| 1 x I2C TTL | |
| 1 x SPI TTL | |
| 1 x cassette (not yet implemented) | |
| 1 x earphone (not yet implemented) | |
| 4 x protected digital input 12V | |
| 4 x open collector output | |
| 4 x NO/NC relay contact output | |
| 2 x analog input 0-10V (not yet implemented) | |
| 2 x analog output 0-10V (not yet implemented) | |
| power outputs | +12/5/3.3V 3A |
| -12/5V 0,5A | |
| others | RTC |
| MPU (manual programming unit) | |
| - 8 data and 16 address switch | |
| - 8 digits hexadecimal LED display | |
| (partly implemented) | |
| power supply | ATX 600W |
| OS | Digital Research CP/M v2.2 |
| Z-System |
The machine is housed in a power supply unit (OMSZÖV OE-222) from the 1980s. The computer consists of the following components:
| name | function |
|---|---|
| SC126 | motherboard (Stephen C. Cousins) |
| SC702 | RCBus backplane (Stephen C. Cousins) |
| SC715 | RCBus CF module (Stephen C. Cousins) |
| SC716 | RCBus SIO-2 module (Stephen C. Cousins) |
| SC717 | RCBus PIO module (Stephen C. Cousins) |
| SC718 | RCBus CTC module (Stephen C. Cousins) |
| SC719 | RCBus DIO module (Stephen C. Cousins) |
| PIOI | I/O interface module |
| PMAN-DP | Display module |
| PMAN-SW | Switch module |
| PPOW | Power distribution module with external fuses |
| PSPK | Speaker amplifier module with speaker |
| 2 x TTL/RS232 level shifter module | |
| ATX PC power supply |
| name | function |
|---|---|
| PANA | Two channels analog input-output module (0-10V) |
| PCAS | Cassette interface module |
| PCOX | Internal COVOX-style mono sound module with earphone amplifier |
| PMAN-IF | Manual programming interface module |