Dual Serial / 80 Column Board (Prototype)

A prototype expansion card for the Coleco ADAM combining two serial ports with an 80-column display, aimed squarely at running CP/M on the machine: 80 columns is what CP/M software of the period was written for, and the ADAM's stock display gives 31.

The design goals

• Be compatible with the Micro Innovations serial card, so existing software would find it where it expected to.
• Carry two serial ports on one card rather than one.
• Take daughter boards, which is how the AY sound, parallel interface and boot PROM cards in this catalogue attach.

The design was worked through in public on the AtariAge forum from 2019 by Charles Lane - charlesmouse - including a schematic and layout, and an idea for integrating a Raspberry Pi Zero. This entry is the prototype rather than a production card.