Tandy TRS-80 Model I

The Tandy TRS-80 Model I launched as a ready-to-use package containing the keyboard computer, monochrome display and cassette recorder. Its Z80 processor, BASIC in ROM and comparatively low price made personal computing accessible through Radio Shack stores.

Alongside the Apple II and Commodore PET, it formed the 1977 group of mass-market personal computers and created a large software and hardware ecosystem.

Notable Features

• Zilog Z80 at 1.774 MHz with 4KB standard; expandable to 16KB internally and 48KB with Expansion Interface.
• The principal display was External 12-inch monochrome monitor; 64 x 16 text.
• Storage support consisted of Cassette; optional 5.25-inch floppy drives through Expansion Interface.

Historical Significance

• Alongside the Apple II and Commodore PET, it formed the 1977 group of mass-market personal computers and created a large software and hardware ecosystem.
• Radio Shack’s large retail network made demonstration, sales and support available well beyond specialist computer dealers.

Collector’s Notes

• Factory memory, drive configuration and regional badge should be checked because many surviving systems were upgraded.
• Original monitors, manuals, software, storage hardware and Radio Shack peripherals add historical context.

Specifications

Technical Information
Name	Tandy TRS-80 Model I
Manufacturer	Tandy
Launched	Wednesday, August 3, 1977
Discontinued	January 1981
Launch Price	$599.95 complete system
Country	United States
CPU	Zilog Z80 at 1.774 MHz
Units Sold
Operating System	Level I or Level II BASIC; TRSDOS with floppy drives
CPU Speed	1.774 MHz
RAM	4KB standard; expandable to 16KB internally and 48KB with Expansion Interface
ROM	4KB Level I BASIC or 12KB Level II BASIC ROM
Display	External 12-inch monochrome monitor; 64 x 16 text
Graphics	128 x 48 block graphics
Sound	One-bit audio through cassette output
Storage	Cassette; optional 5.25-inch floppy drives through Expansion Interface
Keyboard	Integrated 53-key keyboard
I/O	Cassette, video, expansion bus; Expansion Interface adds floppy, printer and optional RS-232