Tandy TRS-80 Model 100

Manufactured by Tandy Corporation and sold through Radio Shack, the TRS-80 Model 100 was a portable computer equipped with Microsoft-written ROM software and a built-in auto-dial modem, offered in 8K and 24K RAM configurations with an entry price of $339²⁴⁶.

The Model 100 shipped with five built-in management programs: a personal word processor, appointment calendar, address book, phone directory, and telephone auto-dialer, all stored in read-only memory bearing a 1983 copyright by Microsoft Incorporated¹⁵. These tools, combined with the ability to write custom BASIC programs, positioned the machine as a self-contained productivity device for mobile professionals⁵. Its ROM-based software suite eliminated the need for external storage to begin working, a notable advantage in field use where floppy drives or cassette systems were impractical.

The technical reference manual identifies the CPU as the 80C85, though no clock speed is documented in surviving materials¹. Support for serial communication is confirmed via inclusion of "RS-232C Signals" in the manual’s table of contents, and the IM6402 UART is explicitly referenced in control word documentation¹. Memory components listed include the TC5518BF-25 and the LH-535618, though their exact configuration and total usable memory beyond the 8K and 24K system options remain unspecified¹.

Power was supplied via batteries or an optional AC adapter, and its form factor was designed to fit in a briefcase, underscoring its role as one of the earliest true portable computers⁵. The built-in modem allowed direct connection to information services or remote computers from any telephone line, a capability marketed as essential for journalists and business travelers⁵.

Pricing discrepancies appear across contemporary sources: while two issues of The Rainbow list the 24K Model 100 at $510, a third cites $425, suggesting either a price cut, regional variance, or promotional discrepancy within a single year²⁴⁶. The BOOSTER PAK accessory, advertised as providing up to 2 megabytes of additional RAM and/or ROM, was marketed for both the Model 100 and Model 102, indicating a shared expansion ecosystem³.

The machine was grouped in product listings with the Model 4, Model 4 Portable, Tandy 1000, Tandy 1200, and Model 2000, but no documentation establishes technical lineage or shared architecture²⁴⁶. At a Tandy Assembly event, the Model 100 was mentioned alongside "Model 100s" and pocket computers, hinting at a broader categorization of compact computing devices within Tandy’s internal taxonomy¹¹.

The hardware bore a 1983 copyright by Tandy Corporation, and the software a concurrent copyright by Microsoft, marking one of the more visible collaborations between the two companies in the embedded systems space¹. Despite its capabilities, the surviving documentation is silent on critical specifications including weight, dimensions, display characteristics, sound, storage media, expansion buses, and operating system nomenclature, gaps that reflect the era’s tendency to prioritize usability over technical disclosure.

Specifications

References

1. TRS 80 Model 100 Technical Reference Manual
2. The Rainbow Vol. 04 No. 07 - February 1985 (1985)
3. TS CAT V3N1
4. The Rainbow Vol. 04 No. 08 - March 1985 (1985)
5. How to Relax and Enjoy Your Home & Personal Computer - Editors of PC Retailing Magazine
6. The Rainbow Vol. 05 No. 01 - August 1985 (1985)
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