This is an attempt to catalogue everything Gemini/80-BUS. 🙂


Nascom was in serious trouble financially, so a decision was made to develop a new system called “Multibus”, using the old NASBUS but renaming it to 80-BUS (I assume) to avoid problems with the receivers. Existing suppliers were brought on board and a common numbering system was started. Two new boards were designed, the G811 CPU and G812 RAM, to replace the Nascom-1 and Nascom-2 which were, of course, Nascom property. G8 stood for Gemini 8(0-BUS compatible) and it was followed by a 2-digit number for the board. The numbers were issued in order of release. G812 was the last of the old numbering system, being the last board designed for the NASBUS.

With the formation of Gemini (just as Lucas bought Nascom, creating Lucas-Nascom) the prefixes changed to GM to signify Gemini Multibus. The idea was that the boards with the GM prefix would have been type-tested in typical Gemini systems and could, in most cases, be able to work together in the same system. Obviously there were exceptions – you couldn’t use two CPU cards for example.

Some of the numbers kept a code indicating the actual supplier rather than the G or GM, but the number is still a Gemini one.

CC – Climax Computers Ltd. South Molton, Devon
EV – EV Computing Ltd. Burnage, Manchester
IO – IO Research Ltd. Mill Hill, London
MP – Microcode (Control) Ltd. Clitheroe, Lancashire
AM – Arfon Microelectronics Ltd.

Something that confused me initially was WT (Winchester Technology), who produced:
WT100 – Prototyping board
WT625 – Teletext colour graphics board
WT910 – Nasbus sound card
These have a similar numbering scheme but they are not Gemini numbers.

The GM prefix supposedly signified that a product was tested and proved to work on the 80-BUS with other 80-BUS components.

Some parts were re-numbered and I suspect that this was to move them into a “tidied up” sequence. I’ve put this list in numerical order rather than component type order as is shown in price lists and catalogues as I think it gives a better idea of how the numbering system worked.

I’ve left gaps where there are one or more missing numbers. If you can help fill those gaps I’d be very grateful to hear from you.

Manuals & Literature
GM301 – Z80 CPU manual
GM302 – Z80 PIO manual
GM303 – NAS-SYS 3 manual

GM306 – GM811 CPU Hardware manual
GM307 – GM811 RP/M Software manual

GM310 – GM803 EPROM hardware manual
GM311 – GM802 RAM hardware manual

GM314 – GM517/518 GEM-ZAP software manual
GM315 – GM519/521 GEM-PEN manual
GM316 – Gemini Galaxy manual
GM317 – GM524/525 GEM-DEBUG manual
GM318 – GM813 CPU Hardware manual
GM319 – CP/M 2.2 manuals (Digital Research)
GM320 – Z80 CTC manual
GM321 – GM816 I/O board hardware manual
GM322 – GM829 FDC/SASI hardware manual
GM323 – MultiNet Workstation user manual
GM324 – MultiNet Workstation system manual
GM325 – MultiNet Installation manual
GM326 – MultiNet Superstation user manual
GM327 – GM386 OEM manual
GM328 – M-F-B Software manual
GM329 – GM818 Serial daughter board instruction manual
GM330 – GM832 SVC Software manual
GM331 – GM832 SVC Hardware manual
GM332 – GM837 Colour board users manual
GM333 – GM860 EPROM programmer users manual
GM334 – GM833 500k RAM disk user manual
GM335 – GM848 Serial & parallel I/O board user manual
GM336 – Z80 SIO manual
GM337 – GM824 8-bit A/D board user manual
GM338 – CP/M-86 manual
GM339 – GSX manual
GM340 – DR-Draw manual
GM341 – DR-Graph manual
GM342 – C-BASIC manual

GM406 – 12in monitor -green

GM411 – Hi-res colour monitor

GM413 – Digitiser pad with pen
GM414 – Digitiser pad with cursor
GM415 – 8in DS drive in case with power supply
GM416 – 2x 8in DS drive in case with power supply
GM417 – 8in DS drive & 3.5″ DS drive in case with power supply
GM418 – 3-pen A4 plotter

Software / Operating systems
GM512 – CP/M 2.2 DDDS (809/829+815)

GM517 – GEM-ZAP (GM821/827+812) – tape
GM519 – GEM-PEN (GM812) – tape

GM524 – GEM-DEBUG – tape


GM530 – List/Repair DDDS CP/M
GM531 – CopySB DDDS CP/M
GM532 – CP/M 2.2 QDSS (809/829+825)

GM537 – RP/M V2 for GM811/GM813
GM542 – List QDSS CP/M
GM543 – IVC-MON V2 for GM812
GM545 – The Last One DDDS CP/M
GM546 – The Last One QDDS CP/M
GM547 – IVC Graphpac DDDS CP/M
GM548 – IVC Graphpac (Links MBASIC) QDSS CP/M
GM549 – Economy BASIC (GM812) – tape
GM550 – Economy BASIC DDDS CP/M
GM551 – Economy BASIC for IVC QDSS CP/M
GM552 – Config DDDS CP/M

GM555 – CP/M 2.2 QDDS (809/829+825)

GM557 – MBASIC interpreter QDSS CP/M
GM558 – dBase II QDSS CP/M
GM559 – WordStar QDSS CP/M
GM560 – MailMerge QDSS CP/M
GM561 – SpellStar QDSS CP/M
GM563 – Source listing – CP/M 2.2 BIOS QDSS CP/M
GM564 – Source listing – IVC-MON V2 QDSS CP/M
GM565 – Source listing – Format/Backup utility QDSS CP/M
GM566 – Source listing – Config QDSS CP/M
GM567 – Source listing – SysWin / FormWin QDSS CP/M
GM568 – Source listing – SIMON boot rom QDSS CP/M
GM569 – SIMON for GM811/GM813
GM570 – COMPAS version 3 QDSS CP/M
GM571 – Sapphire Calcmaster QDSS CP/M

GM573 – Pluto Quickdraw QDSS CP/M
GM574 – Economy BASIC for SVC QDSS CP/M
GM575 – SVC Graphpac (Links MBASIC) QDSS CP/M
GM576 – Wordstar Professional QDSS CP/M

GM578 – CP/M-86 QDSS ((809/829+888+825 or Galaxy + 888)
GM579 – Digital Research GSX (Pluto) QDSS CP/M
GM580 – Digital Research DR-Draw QDSS CP/M
GM581 – Digital Research DR-Graph QDSS CP/M
GM582 – Digital Research CBASIC QDSS CP/M

G601 – Reset jump kit for the Nascom-1

GM605 – 8″ upgrade kit for GM809
GM609 – 3A PSU enclosure for GM610 frame
GM610 – 19″ Vero frame for 8″ deep boards

G613 – Original number for GM821 – 59-key keyboard

GM615 – PIO cable
GM616 – Serial cable (nascom)

GM619 – 34-way ID/PCB edge connector
GM620 – 4-way ID plug (M)
GM621 – 16-way ID plug (M)
GM622 – 26-way ID plug (M)
GM623 – 34-way ID plug (M)
GM624 – 50-way ID plug (M)
GM625 – 16-way ID socket (F)
GM626 – 26-way ID socket (F)
GM627 – 34-way ID socket (F)
GM628 – 50-way ID socket (F)
GM629 – 26-way rt-angle ID plug
GM630 – 34-way rt-angle ID plug inc ejectors
GM631 – 50-way rt-angle ID plug inc ejectors
GM632 – 77-way edge connector
GM633 – 34-way edge connector
GM634 – edge connector clips
GM635 – 14-pin header plug
GM636 – 16-pin header plug
GM637 – 20-pin header plug

GM639 – DB25P

GM642 – DB15S
GM643 – DB15P
GM644 – Centronics (Amphenol) socket
GM645 – Centronics (Amphenol) plug
GM646 – Gemini parallel keyboard cable – coiled type
GM647 – Keyboard enclosure for GM821

GM649 – 34-way cable assembly (Gemini)
GM650 – 34-way cable assembly (QM2000)
GM651 – Pertec/Micropolis power socket/pins

GM653 – Micropolis 1015F5 drive 400k
GM654 – Motherboard for 5 boards
GM655 – Motherboard for 8 boards
GM656 – Motherboard for 3 boards
GM656 – 19″ frame for full depth boards (nascom) – unsure about number
GM657 – Micropolis 1115F6 drive 800k

GM660 – Gemini video cable
GM661 – Gemini enclosure (excluding card frame assembly)
GM662 – 5-board frame
GM663 – Daughter board assembly for 816 I/O board
GM664 – Keyboard enclosure for GM827
GM665 – Parallel printer cable

GM668 – Keyboard cable assembly (internal)
GM669 – IDS parallel printer cable
GM670 – Set of connectors for GM817 SMPS
GM671 – Kbd case – IVC card cable
GM672 – 100′ 16-way ID cable
GM673 – 100′ 20-way ID cable
GM674 – 100′ 26-way ID cable
GM675 – 100′ 34-way ID cable
GM676 – 100′ 37-way ID cable
GM677 – 100′ 50-way ID cable
GM678 – MultiNet cable 100m
GM679 – MultiNet wall mounting junction box/socket
GM680 – MultiNet 3-pin plug
GM681 – MultiNet BNC plug
GM682 – Motherboard for 6 boards
GM683 – Internal serial printer cable

GM685 – 6-card internal frame assembly
GM686 – 3-card internal frame assembly
GM687 – 3-card enclosure (as GM909 but bare case only)
GM688 – 6-card enclosure (similar to above but 6-card)
GM689 – Fan filter assembly
GM690 – Mains fan (as Gemini)
GM691 – Rodime RO201 5.4MB Winchester drive
GM692 – Rodime RO202 10.8MB Winchester drive
GM693 – Rodime RO203 16.2MB Winchester drive
GM694 – Rodime RO204 21.6MB Winchester drive
GM695 – Xebec Winchester Controller board
GM696 – Fan filter
GM697 – MultiNet 3-pin socket

GM699 – Serial cable for digitiser pad
GM700 – Mini pallette to Rapier monitor cable

GM702 – Small backplate for Gemini – plain
GM703 – Small backplate for Gemini – MultiNet
GM704 – Small backplate for Gemini – IEEE
GM705 – 26-way cable for GM836 to GM811/GM813
GM706 – Toshiba ND-04D 48TPI DDDS half-height drive 400k
GM707 – Toshiba ND-06D 96TPI QDDS half-height drive 800k
GM708 – Epson SM140 3-1/2″ DS drive 800k
GM709 – Cable for A4 plotter
GM710 – Large backplate for Gemini – Multi RS-232
GM711 – Large backplate for Gemini – 4x DB25
GM712 – Large backplate for Gemini – 34W + 2x 50W IDS
GM713 – Large backplate for Gemini – 16W + 2x 26W IDS
GM714 – Set of cables for Gemini IVC-SVC conversion
GM715 – 50-way ID/PCB edge connector
GM716 – MultiNet 1m spur (e.g. Workstation to wall box)
GM717 – Cable for colour workstationto Rapier monitor
GM718 – Small backplate for Gemini – 34W + 50W IDS
GM719 – Set of connectors for GM843 SMPS

GM723 – Ultra high capacity floppy drive. Manufacturer went bankrupt.
GM724 – Set of connectors for GM850 SMPS
GM725 – Cable for Pluto to Rapier monitor
GM726 – Large backplate for Gemini – plain
GM727 – Full height bezel for Toshiba drives

Multiboard Products
G801 – Mimi computer – not an 80-BUS system
G802 – “RAM64” 64k dynamic RAM board
GM802K – kit of above
CA802/1M – upgrade kit – expands CA856 to 1MB
G803 – EPROM/ROM board
GM803K – kit of above
G804 – Disk power supply
GM804K – Disk PSU kit
G805 – Henelec disk system kit
GM805-1 – ready-built & tested Gemini version of the G805 with 1 drive
GM805-2 – ready-built & tested Gemini version of the G805 with 2 drives
G806 – “Supermum” buffer board
G807 – 3A linear PSU
G808 – EPROM programmer kit original number
GM808K EPROM programmer kit (Bits n’ PCs. Does not plug into bus)
G809 – FDC board for GM815 drives
G810 – Combined PSU & motherboard kit
GM810K – Combined PSU & “Hypermum” motherboard kit
G811 – Z80 CPU + ROM board
G812 – IVC video board
GM813 – Z80 CPU + 64k RAM board
EV814 – IEEE 488 interface board
GM815-1 – Floppy drive – like GM805-1 but without disk controller
GM815-2 – Dual floppy drives – like GM805-2 but without disk controller
GM816 – I/O Board (RTC, CTC, 3x PIO)
GM817 – 85W (6A) SMPS – up to about 5 boards + 2x 5.25″ fdd
GM818 – Serial I/O daughter board for GM816
AM819 – Speech board
AM820 – Light pen
GM821 – 59-key keyboard
GM822K – Real time clock kit (connects to PIO)
GM823 – GM827 keyboard – Danish / Scandinavian version
GM824 – 8-channel 8-bit A/D board – was IO824
GM825-1S – Floppy disk sub-system 1x 400k
GM825-2S – Floppy disk sub-station 2x 400k
GM825-1D – Floppy disk sub-system 1x 800k
GM825-2D – Floppy disk sub-system 2x 800k
MP826 – 32k static RAM board
GM827 – 87-key keyboard
IO828H – “Pluto” 768×576 colour graphics board
IO828L – “Pluto” 640×576 colour graphics board
GM829 – 5.25″ + 8″ FDC + SASI interface board
IO830 – Mini-pallette expansion board for “Pluto”
GM831 – 5-slot backplane
GM832 – SVC video board
GM833 – 500k RAM disk
GM833/2M – 2MB upgrade for GM833
GM834 – GM827 keyboard – German version
GM835-5 – Winchester sub-system 5.4MB
GM835-10 – Winchester sub-system 10.8MB
GM835-16 – Winchester sub-system 16.2MB
GM835-20 – Winchester sub-system 20MB
GM836 – Multinet network board (board only)
GM836UPG – GM836 for upgrade to Superstation
GM836OEM – GM836 with transport software & manual
GM837A – (was CC837 – Climax colour) 256×256 colour graphics video board (PAL)
GM837B – (was CC837 – Climax colour) 256×256 colour graphics video board (PAL + RGB)
GM838 – GM827 – French (AZERTY) version
GM839 – Prototyping board
MP840 – 14-slot backplane with ground plane & termination – became NE840 later
NE840 – Microcode pulled out of the 80-Bus market, Newburn took over
GM841 – Extender board
GM842 – D-A converter for GM816
GM843 – 10A SMPS
GM844 – 8-way motherboard with connectors
GM845 – 6-way motherboard with connectors
GM846 – 3-way motherboard with connectors
BE847 – Arithmetic board (Belectra HSA-88B – uses AM9511)
GM848 – Serial + Parallel I/O board
GM849 – Advanced FDC/SASI board
GM850 – 5A SMPS
GM851 – 12-bit A/D board 16 S/E or 8 differential inputs
GM852 – low profile 87-key keyboard options: SE,PE,SD,PD,SF,PF,SG,PG,SS,PS
GM853 – “Bytewide” EPROM board
GM854 – 85W SMPS
GM855 – Tape streamer sub-system
GM856 – 8088 256k CPU board
GM857 – 35W SMPS
GM858 – 40W SMPS
GM859 – “Pluto” pallette board
GM860 – “Bytewide” EPROM programmer (does not plug into bus)

GM862 – 256k dynamic RAM board
GM863-32 – 32k static RAM board with battery backup
GM863-64 – 64k static RAM board with battery backup
IO864 – Pluto 2 graphics board
GM865 – half-height 8″ drive sub-system
CA866 – 8088 128k CPU board
GM867 – Opto-input board
GM868 – Pluto 2 frame grabber
GM869 – Opto-output board
GM870 – Modem board
GM871 – Tape streamer controller
NE871 – 32 opto input board
VS872 – Video frame grabber
GM873 – 2MB RAM disk card
NE874 – 16-channel A/D card
NE875 – 16-channel D/A card
NE876 – 64-channel digital input board
NE877 – 64-channel digital output board

GM879 – Falcon graphics card
GM880 – 64180 (Z180) CPU/RAM card

GM885 – Winchester sub-system
GM886 – 80286 1MB CPU board

GM888 – 8088 co-processor board
NE889 – 512k static RAM with battery backup
GM890 – Z280 CPU/RAM board – development cancelled. Replaced by NE898
GM891 – V21/V22 modem board

NE898 – 64180 (Z180) CPU/RAM board. Plug-in replacement for GM813.

GM903 – Gemini Galaxy 2 Computer with 2x 400k drives
GM904 – Gemini Galaxy 2 Computer with 1x 400k drive
GM905 – Gemini Galaxy 2 Computer with 2x 800k drives
GM906 – Gemini Galaxy 2 Computer with 1x 800k drive
GM907 – Gemini Galaxy 3 Computer with 1x 5.4MB + 1x 800k drives
GM908 – Gemini Galaxy 3 Computer with 1x 10.8MB + 1x 800k drives
GM909 – Gemini Galaxy 4 MultiNet workstation
GM910 – Gemini Galaxy 4 MultiNet file server with 1x 5.4MB + 1x 800k drives

GM912 – Gemini Galaxy 4 MultiNet file server with 1x 10.8MB + 1x 800k drives

GM914 – Gemini Galaxy 3 Computer with 1x 16.2MB + 1x 800k drives
GM915 – Gemini Galaxy 4 MultiNet file server with 1x 16.2MB + 1x 800k drives
GM916 – Gemini Galaxy MFB (has GM829 controller) 5.4MB + 96TPI DS + 48TPI DS

GM921 – Gemini Galaxy MFB (has GM829 controller) 16.2MB + 96TPI DS + 48TPI DS
GM922 – Gemini Galaxy 96TPI SS + 96TPI DS + 48TPI DS
GM923 – Gemini Galaxy 4 Colour workstation (including Pluto)
GM924 – Gemini Galaxy 3 Computer with 1x 21.6MB + 1x 800k drives
GM925 – Gemini Galaxy MFB2 (has GM849 controller) 1x10MB+360k+720k+720k 3.5″

GM927 – Gemini Galaxy 4 MultiNet file server with 1x 20MB + 1x 800k drives


Nascom Pages