Ferguson Big Board

The Big Board (1980) and Big Board II (1982) were Z80 based single-board computers designed by Jim Ferguson. They provided a complete CP/M compatible computer system on a single printed circuit board, including CPU, memory, disk drive interface, keyboard and video monitor interface. The printed circuit board was sized so as to allow attachment to an 8 inch floppy disk drive. The Big Board II added a hard disk drive interface, enhancements to system speed (4 MHz vs. 2.5 MHz) and enhancements to the terminal interface.[2]

One version of the Big Board was used in the Xerox 820.

Big Board I

- Z80 CPU at 2.5 MHz.
- 64 KB dynamic RAM in 32 4116s or equivalent.
- An ASCII keyboard interface.
- A TTL / composite video CRT interface allowing a display of 24 lines by 80 characters.
- A SS/SD floppy disk interface allowing addition of up to four 8" Shugart Associates SA800 compatible 8" floppy disk drives.
- Two (optional) RS-232 serial ports.
- A parallel Centronics compatible printer port.
- An optional real time clock.
- Board dimensions 8.5" (215 mm) by 13.75" (349.3 mm). (Compare to SA-800 disk drive: 9.5" x 14.5".)

Big Board II

- Z80 CPU at 4 MHz.
- 64 KB dynamic RAM in 8 4164s or equivalent.
- SASI/SCSI hard disk interface, also usable as a general purpose I/O or for control of other SCSI devices.
- An ASCII keyboard interface.
- A TTL / composite video CRT interface allowing a display of 24 lines by 80 characters.
- A DS/DD floppy disk interface allowing addition of up to four 8" or 5.25" floppy disk drives.
- Two RS-232 serial ports via a Z80 SIO.
- A parallel Centronics compatible printer port via a Z80 PIO.
- An optional real time clock.
- Board dimensions 8.875" (225.4 mm) x 14.5" (368.3 mm)
- 6 ROM/EPROM sockets, including ability to program EPROMs in place.