Model 4 emulation card: Fact or fiction?

written by Matthew Reed

Trackstar 128

Radio Shack advertisement for the Trackstar 128, an Apple IIc emulator card

After Radio Shack introduced their MS-DOS compatible Model 1000 series, there were persistent rumors about a Model 4 emulation card that was being developed. Such a board would have been an clever way to help migrate Model 4 customers to the newer MS-DOS computers. Some people were even told at their Radio Shack stores that a Model 4 emulator would be released soon. But it never happened and no type of TRS‑80 emulator was ever released by Radio Shack.

At the time, Radio Shack sold the Trackstar 128, an Apple IIc emulator card created by Diamond Computer Systems. The Trackstar used actual Apple II ROMs (licensed from Apple) along with custom hardware to achieve nearly 100% Apple compatibility. So the concept of a Model 4 emulation card certainly must have occurred to people at Radio Shack.

I’ve had three different people write to me (years apart) recalling details of a Model 4 emulation project that Radio Shack worked on but pulled at a very late stage. Their accounts match in almost all the details.

According to these people, the goal was compatibility with all of the Model 4 and Model III software sold by Radio Shack. The unnamed card was intended as an add-on for the Model 1000 and contained a Z80 CPU, floppy disk controller, video generation circuitry, and enough logic to process the memory and I/O. It used the Model 1000’s memory, keyboard, monitor, printer port, and floppy drives. It even supported the extra 64K of Model 4 banked memory.

Most of the Model 4 emulation was handled by the card hardware and the rest by the accompanying MS-DOS software. The Model 4 ROM was included within the MS-DOS software, and there were plans to include TRSDOS 6 (for the Model 4) and TRSDOS 1.3 (for the Model III) with the package.

Even though the goal was only compatibility with Radio Shack software, the card was able to run all software that was tried. One person recalled seeing a demonstration of Model III Sea Dragon and other self-booting TRS‑80 games.

So did such a Model 4 emulation card ever exist? Is it possible that all three people were confusing it with another project?

At this late date, there is probably no way to ever know for sure.

Categories: History