gm812

This was a very clever card at the time. The IVC (Intelligent Video Controller) had only a mono display, but the resolution was variable. It made an excellent display card as it could emulate the standard Nascom display and also display graphics. The cost was also reasonable (as these things went at the time!) so it proved to be very popular.

It was well named, as it included its own Z80 processor, 2kB RAM, CRTC chip and operating system in EPROM. This made it independent of the main Z80. Only 1kB of the RAM was actually used, the remainder could run user programs.

An unusual addition was a parallel keyboard input. (Gemini GM821 Cherry 59-key or GM827 Rotec 87-key). The latter had user-definable keys. It was thus possible to build quite a nice system using just this card with a G811 processor/RAM card or G813 CPU/64k RAM/Video card!

Dedicated Z80A processor
6845 graphics control processor
80 characters 25 line mono main display
Second width-programmable mono display (supplied as 48x25)
Inverse display possible
128 Programmable character generator
128 Fixed characters in ROM
160x75 "pixel" graphics
Keyboard input (with user-definable keys)
Combined video output (not via an RF modulator)

This card was designed to run without using the main computer's memory. A system of commands was sent to the board via three I/O ports. Because of this, existing software using the NASCOM memory-mapped display would not work.

An unusual choice of connector was used for the video output. If you look at the top of the card in the picture you can see a standard 1/4 inch "jack" plug - not normally associated with video signals!