All the following were, at some time, sold under the Gemini name. Many of them were not actually manufactured by Gemini though. The expansion boards were all Nas-bus compatible, although the bus had now been renamed as the 80-BUS. The frames offered would only really accept the Gemini cards, as they were intended for the 8in x 8in format only rather than the 8in x 11in NASCOM computers. However, a NASCOM-2 would work as the CPU card even though it stuck out of the frame by 3in! The NASCOM-1 was of no use really as it needed special arrangements to fit it to the frame (but see the pictures of my machine to see how it was done!). The frames and motherboards were sold separately, so the motherboards were suitable for NASCOM systems if used without the frames. (Of course, many NASCOM systems DID fit into Gemini frames – the frame was never the same again though. You can work wonders with a bit of aluminium and a hacksaw!)

Many of the Gemini expansion boards were unsuitable to the NASCOM-1 due to insufficient I/O decoding on the main board. Also the lower clock speed of this machine meant that it couldn’t really be used with disk systems. However, with a bit of hardware modification and a little luck in running the NASCOM-1 at 4MHz, both these problems were solvable.

Several of the cards are coded Gnnn on the actual card, whereas they are advertised as GMnnn. This may be irrelevant, but I thought I’d better mention it. Where other codes, e.g. EV are used they are for a manufacturer other then Gemini.

The official numbering for Gemini products was GMxxx. The idea of the 800 series was that they were already built and tested, all the components would work together (in theory – it’s probably impossible to test every combination fully) and there was software support to enable them to do so. The numbers were issued in order of development.

Note that the Gemini Galaxy 2 and Quantum 2000 computers were advertised as using two Z80 processors. They didn’t happen to mention that only one was used as the system processor and the second as the graphics processor. Was this the beginning of “imaginative advertising” in computers?

I’ve included various pages of information; pictures, circuit diagrams etc. Almost all of these are items in my collection. However, there is a lot of information that I don’t have. One of the best (and only!) sites that I’ve found for 80-Bus stuff in particular is 80bus.co.uk (opens in a new window/tab) where Richard has archived some very nice stuff.

Gemini Galaxy 2 GM903 Complete system with 2 floppy drives
Gemini Quantum 2000 Complete system
19in Frame GM610 Not intended for use with the NASCOM system as it only accepted 8 inch deep cards.
19in Frame GM656 Suitable for use with all systems.
5-Slot Motherboard GM654 Suitable for use with all systems.
8-Slot Motherboard GM655 Suitable for use with all systems.
5-board frame GM662 Not intended for use with the NASCOM system as it only accepted 8 inch deep cards.
g682 GM682 Suitable for use with all systems.
Ready-built GM801 A complete 64k dual disk CP/M computer designed by Gemini and later sold to British Micro, who sold it as the “Mimi”
DRAM card GM802 64k dynamic RAM card
EPROM Board GM803 Sold without EPROMs!
Disk controller GM805 48TPI cased system connected via the PIO
3A Power Supply GM807
EPROM programmer GM808 Re-badged version of the Bits’n PCs unit. For 2708 ” 2716 EPROMs
Floppy Disk controller GM809
(dated May 1982)
48/96TPI – replaced later by GM829. This was not suitable for use with the NASCOM-1 due to the slow processor.
CPU Board GM811 with 4 RAM/EPROM sockets (no RAM fitted)
IVC Card GM812 Intelligent Video Controller – 80 char/25 lines
G813 Processor GM813 with RAM and CP/M compatible
IEEE488 board EV814
Multi I/O board GM816 with 6 I/O ports, 4 CTC, RTC
6A Power Supply GM817 switch mode type
Twin Serial Port GM818 daughter board to fit G816 I/O board
Keyboard GM821 59-key ASCII parallel interface keyboard with cursor keys
RTC board GM822 Real-time clock kit – plugs into PIO
A-D board GM824 Re-badged version of an IO Research unit.
Floppy drive unit GM825-1S
or GM825-2S
1 or 2 5.25in floppy drive unit
Keyboard GM827 Parallel interface keyboard with cursor and function keys
Static RAM board MP826 32k static RAM with battery backup
87 key keyboard GM827 with user-definable function keys + numeric pad
Disk Controller board GM829 Gemini – for 4 mixed 5.25in and 8in + SCSI HDD (Someone said that this was also used in the Lucas Logic “Winchester” hard disk drive!)
SVC Video Card GM832 Super Video Controller (enhanced IVC)- 80 char/25 lines
RAM Disk GM833 512k dynamic RAM. Virtual disk operation.
“Winchester” drive GM835 5.4Mb (!) hard disk drive subsystem (1450 UK Pounds in 1983!)
Network Adapter GM836 Adaptor for their proprietary networking system.
Colour vector graphics GM837 Re-badged version of a Climax board. 256×256 display. 16 colours. Much cheaper than the PLUTO system!
Prototyping card (58k) GM839
14 Slot Motherboard MP840
80-BUS card extender (164k) GM841
10A Power Supply GM843 switch mode type
Serial Card GM8484 4 serial ports + PIO
Disk Controller GM849 also supports 1.2M drives – up to 8 devices
Keyboard GM852S Serial interface keyboard with cursor and function keys
EPROM Programmer GM860 “Bytewide” programmer with built-in mains supply.
Monitor Badged 12in Phoenix unit with green or amber phosphor.
PLUTO Graphics IO828 High power (for the time) graphics board. This was a basic version of the IO Research board.
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