The Norcom TC-III
The Model III added some nice improvements to the Model I and boasted nearly complete compatibility. But there were still some areas of incompatibility. Considering that most TRS‑80 software development moved to the Model III, it was understandable that many Model I owners felt left behind.
The Norcom TC-III was a $399 ($499 factory installed) motherboard replacement for the Model I that promised all Model III features right in the Model I case. It was sold by Northern Information Technology Corp. The advertisements touted the following features:
- Uses Model I keyboard, case, monitor and power supply
- Includes full 48K memory, disk controller, printer and external I/O ports same as Model III
- All Model III features plus reverse video and output to drive external speaker with no additional hardware
- Uses Model III BASIC ROMs or other EPROMs
- Runs Model III software
- No Expansion Interface needed – it’s all built in
- RS-232 add-in accessory board available
Although not explicitly stated by the advertisements, it appears that the TC-III was able to use a Model I owner’s existing external floppy drives. That means that a TC-III upgrade would have amounted to a substantial cost savings over buying a Model III with floppy drives. A motherboard upgrade is a common idea today, but it was pretty novel at the time.