Digital Group Video Card

The Digital Group Video Card was one of the earliest practical video display interfaces for hobbyist microcomputers in the mid-1970s. Designed by **Dr. Robert Suding** and published in the Digital Group newsletter, it allowed builders to add a real CRT display to early systems like the Mark 8. In the MicroBasement, this card represents the pioneering spirit of 1970s homebrew computing — a simple, build-it-yourself terminal that turned a TV into a usable video display without expensive commercial hardware. This write-up covers its history, publication, specifications, design for the Mark 8, and legacy.

History and Publication

The Digital Group was founded in 1974 by Dick Bemis and Dr. Robert Suding in Denver, Colorado. Suding, an engineer and frequent contributor to hobbyist magazines, designed the Video Card as a low-cost solution for early 8008 and 8080 systems. The complete plans — including schematics, parts list, and construction details — were published in the **Digital Group Newsletter** (issues around 1975–1976). This open, magazine-style publication model was typical of the era and helped thousands of hobbyists build their own video terminals.

Specifications

The card was built entirely with TTL logic (no microprocessor on the board) and used the following key components:

• Display: 8 lines ื 16 characters (5ื7 dot matrix)
• Character Generator: MCM6571 (Motorola 5ื7 dot matrix ROM)
• Memory: 1101 static RAM ICs (256-bit chips, multiple chips for screen buffer)
• Video Output: Composite video for standard TV or monitor
• Interface: Simple parallel interface (direct connection to Mark 8 or similar systems)
• Power: Requires external +5 V and -9 V (no onboard regulators)
• Construction: Single PCB with TTL logic chips, shift registers, and counters

It supported basic cursor control and scrolling, making it a major upgrade over LED displays or Teletype machines.

Designed for the Mark 8

The card was specifically created to work with the **Mark 8** (Jonathan Titus’ 1974 8008-based computer). The Mark 8 had no built-in video, so the Digital Group card provided a practical, low-cost display solution. It connected via the Mark 8’s parallel I/O ports using a simple parallel interface. Hobbyists could build the card and have a working terminal for programming and data entry — a huge leap forward in 1975–1976.

Legacy

The Digital Group Video Card was a pioneering project that showed hobbyists could build real video terminals at home using common TTL chips and 1101 memory. It helped bridge the gap between crude LED displays and modern monitors, inspiring many to pursue careers in computing. In the MicroBasement, it stands as a testament to the open, collaborative spirit of the 1970s homebrew era — a time when a newsletter article could give you a working video display for your Mark 8.

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