g811
This was Gemini’s first processor card, later replaced by the GM813. It was intended to replace a NASCOM-1 or NASCOM-2 as the CPU on a NAS-BUS system and to be the main CPU on the 80-BUS. With the advances in technology since the NASCOM-1 days, Gemini had, effectively, put the CPU and RAM system together on the same PCB. This board did not have the expansion capability of a NASCOM-2 though.This PCB could use either serial or parallel keyboards. I’m not sure if this included the original NASCOM keyboards – I suspect not.The processor was the tried and trusted Z80A running at 2 or 4MHz. It was fitted with 64k of dynamic RAM.The monitor fitted as standard was an early version (often 0.1) of a 4k ROM called RP/M – Rom Program for Microcomputers (written by the writer of NAS-SYS). This looked, to programs, like a CP/M operating system. It was possible to write, run and debug small CP/M applications without having a disk drive installed! These could then be re-loaded from tape when disks became available. Indeed, Microsoft’s MBASIC for CP/M would run if loaded from tape or EPROM.

Unfortunately I have very little documentation on this board. If anyone can help, please contact me. I am looking for the circuits and manual(s).