39-year-old Radio Shack laptop gets new CPU, keeps original screen

Enlarge / A 1983-era TRS-80 Model 100 as an motion hero, dramatically exploding onto the scene.

Faced with a damaged Radio Shack laptop from 1983, IEEE Spectrum editor Stephen Cass did not throw it away. Instead, he pulled out the logic board and changed it with a contemporary microcontroller so he might management the classic screen. Cass wrote about his journey intimately for Spectrum final week.

Cass carried out his operation on a Radio Shack TRS-80 Model 100—one of many first laptops ever produced—which contains a one-piece “slate” kind designed by Kyocera and launched because the NEC PC-8201 in Japan. Its declare to fame was not solely its small moveable dimension (at 2 inches thick and three.9 lbs), however having an amazing keyboard paired with its capacity to run for as much as 20 hours on 4 AA batteries.

The Model 100 features a 2.4 MHz Intel 80C85 CPU, 8 to 32K of RAM, and an eight-line, 40-character monochrome LCD with no backlight. It does not sound like a lot in comparison with right now’s moveable beasts, however journalists liked the Model 100 as a result of they may comfortably write tales on the go utilizing its built-in textual content editor. It additionally included Microsoft BASIC, a terminal program, and an tackle e-book in ROM.

Excerpt from a 1983 Radio Shack computer catalog page featuring the TRS-80 Model 100 laptop.
Enlarge / Excerpt from a 1983 Radio Shack pc catalog web page that includes the TRS-80 Model 100 laptop.

While some folks improve Model 100s utilizing new LCD screens and CPUs (conserving solely the case and keyboard), Cass determined to aim an interface with the moveable’s classic 240×64 pixel show. He discovered it significantly difficult as a result of the pc handles driving the show in an unconventional approach in comparison with right now’s LCD panels.

“The M100’s LCD is definitely 10 separate shows, every managed by its personal HD44102 driver chip,” Cass writes. “The driver chips are every chargeable for a 50-by-32-pixel area of the screen, besides for 2 chips on the right-hand facet that management solely 40 by 32 pixels.” Its designers selected this technique, Cass says, as a result of it hastens textual content show with restricted accessible reminiscence.

After figuring out the protocol for the screen, Cass constructed an interface between the screen and a contemporary Arduino Mega 2560 microcontroller. As the venture stands now, he can show and scroll bitmapped graphics onto the Model 100’s LCD. His subsequent step can be to attempt to interface the screen and keyboard (with a Teensy 4.1 growth board to deal with keyboard communications) to a Raspberry Pi 4 compute module, which might make for a strong moveable machine with a classic really feel.

You can learn extra concerning the technical particulars of his venture on IEEE Spectrum’s web site. Good luck, Stephen!

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