Radio Shack TRS-80 Model III
Introduced:July 1980
Price:US $699 base model
US $2495 w/ 32K, dual drives.
CPU:Zilog Z-80, 2.03 MHz
RAM:4K, 48K max.
Ports:Cassette tape, expansion, serial
Display:12-inch B/W monitor: 64 X 16 text
Storage:0, 1, or 2 internal 178K floppy drives
External cassette @ 500 / 1500 baud
OS:BASIC in ROM, TRS-DOS on disk


The Model III is basically an upgrade of the Model I, which was released three years earlier. It has the same CPU, but it is faster, has more memory, and the floppy drives hold twice as much data, although the Model I could be upgraded to some of these features.

But the major reason for developing the Model III was because the FCC had just instituted new regulations about RF emissions generated by computers and other electronic devices. The Model I was completely unshielded and was unable to pass the emission restrictions.

The Model III system is entirely self-contained. The original Model I had edge-type connectors with ribbon cable connecting the keyboard to the (optional) Expansion Interface, as well as the floppy drives. This type of connection is very unreliable, and led to the occasional system crash or lock-up.

Related Links

  • TRS 80 Hardware Manual Download Page
  • Ira Goldklang's TRS-80 Revived Pages
  • Robert P. VanNatta's comments computer history
  • Tim Mann's TRS-80 Page

    • History of the Radio Shack Computers

    • 1921: - Radio Shack begins as a one-store retail and mail-order company catering to ham operators and electronics buffs.
    • 1963: - Charles Tandy buys the chain of stores, and within two years turned a $4 million dollar loss into a $20 million dollar profit.
    • 1977: August - Radio Shack announces the TRS-80 Model I microcomputer for US$600.
    • 1977: September - One month after launching the TRS-80, 10,000 are sold.
    • 1979: May - Tandy/Radio Shack announces the TRS-80 Model II.
    • 1979: October - Radio Shack begins shipping the TRS-80 Model II to users.
    • 1980: July - Radio Shack introduces the TRS-80 Model III, priced from US$700 to US$2500.
    • 1980: July - Radio Shack introduces the TRS-80 Color Computer, and sells for US$400.
    • 1980: July - Radio Shack introduces the TRS-80 Pocket Computer. Price is US$230.
    • 1981: January - Radio Shack ceases production of the TRS-80 Model I, and recalls units from the US market, due to failure to meet new FCC radio-frequency interference regulations.
    • 1982: January - Radio Shack introduces the TRS-80 Model 16, with 8-inch floppy drives, and optional 8-MB hard drive.
    • 1982: January - Radio Shack introduces the TRS-80 Pocket Computer, Model PC-2, for US$280.
    • 1983: March - Radio Shack announces its TRS-80 Model 100 portable computer. Price is US$799 for 8KB version, to US$1134 for the 32KB version.
    • 1983: May - Radio Shack introduces the TRS-80 Model 4, for US$2000.
    • 1983: October - Tandy/Radio Shack announces the "transportable" TRS-80 Model 4P, for US$1800.
    • 1983: Radio Shack introduces the TRS-80 Pocket Computer, Model PC-4, replacing the PC-1, for US$70.
    • 1983: Tandy releases the TRS-80 Model 2000, which uses the Intel 80186 microprocessor.
    • 1983: Radio Shack unveils the TRS-80 Model 12 at the CP/M '83 Show. Price is US$3200.
    • 1985: March - Radio Shack introduces the Tandy 6000 multiuser system. It features Z80A and 68000 processors, 512 KB RAM, 80x24 text, graphics, 1.2-MB 8-inch disk, optional 15 MB hard drive, TRS-DOS, or XENIX 3.0. It supports up to 9 users.
      Source: Chronology of Events in the History of Microcomputers



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