The TRS-80 Model II

written by Matthew Reed

The Radio Shack TRS-80 Model II

The TRS-80 Model II from a Radio Shack catalog

The TRS-80 Model II was the first in the line of Radio Shack business computers that eventually included the Model 16, Model 12, and Tandy 6000. It was introduced at the June 1979 National Computer Conference1 in New York City. Radio Shack began taking orders that month for delivery in October, shipping 1,000 Model II’s by the end of year.

The introductory price for the Model II was $3450.00 for the 32K version (catalog number 26-4001) and $3899.00 for the 64K version (catalog number 26-4002). A 32K system could be later upgraded to 64K by purchasing the 32K add-on (catalog number 26-4102) for $449.00.

The Model II was actually the second business computer that Radio Shack sold. The previous year, Radio Shack offered the Tandy 10, a relabeled ADDS System 50. The Model II cost less than half the price of the Tandy 10, yet was far more powerful.

Differences from the Model I

After the introduction of the Model II, the TRS‑80 Microcomputer System (introduced in 1977) retroactively became known as the Model I2. Radio Shack saw the Model II as addressing a different market than the Model I:

While Model I3 will continue to fulfill many needs (in some cases it may even be better suited), some of you need more storage, power, and speed than Model I can offer. Rather than stretch the limits of Model I, we decided to meet those additional needs by designing and building a completely new, faster and more powerful computer … TRS-80 Model II.

Unlike the Model I, the Model II was an all-in-one unit with enclosed screen and floppy drives. It came with a Model II specific version of the TRSDOS disk operating system (which wasn’t that similar to Model I TRSDOS) and a powerful version of BASIC. Except for simple BASIC programs, the Model II wasn’t compatible with Model I software. Also unlike the Model I, the Model II had no cassette interface. Radio Shack made it clear that the Model II was not intended as a Model I replacement:

Model II does not replace Model I, rather it’s a new family member, picking up where Model I approaches upper limits of expansion.

They also stated:

We will not be able to accept “trade-ins” of Model I’s for Model II’s.

Radio Shack catalog image

Another Model II image from a Radio Shack catalog


The Model II was more powerful than the Model I:

  • a Z80 running at 4 MHz
  • one double-density 8" drive (expandable to up to four drives)
  • 32K of memory, upgradable to 64K (and later upgradable to 256K)
  • a detachable 76 key keyboard, with HOLD, ESC, BREAK, CTRL, CAPS, REPEAT, F1, and F2 keys
  • one parallel port
  • two RS-232 ports
  • a built-in 12" screen, capable of displaying 80 columns by 24 lines, with uppercase, lowercase, and 32 “business graphics” characters
  • four plug-in card slots

These specifications were quite competitive with other business computer systems, as a Radio Shack catalog pointed out:

Model II compares favorably with systems like IBM’s 51104and costs 33% to 66% less!

The Radio Shack catalog contained several suggested configurations for the Model II, ranging from a $4898.00 “Starter System” with bundled Line Printer II to the $8737.00 “Deluxe 2 Megabyte Business System” with three drives, Line Printer III, metal desk, and printer stand.


Radio Shack sold a wide range of business software for the Model II, including:

  • General Ledger (catalog number 26-4501) for $199.00
  • Inventory Control System (catalog number 26-4502) for $199.00
  • Payroll (catalog number 26-4503) for $399.00
  • Accounts Receivable (catalog number 26-4504) for $299.00
  • Mailing List (catalog number 26-4506) for $79.00

They also offered some very specific business software, such as:

  • Medical Office System (catalog number 26-4508) for $750.00
  • Manufacturing Inventory System (catalog number 26-4509) for $750.00

Radio Shack sold development software and general applications for the Model II, usually for prices much higher than the equivalent Model I versions:

  • COBOL Development System (catalog number 26-4703) for $299.00
  • FORTRAN (catalog number 26-4701) for $299.00
  • Editor/Assembler (catalog number 26-4702) for $199.00
  • Compiler BASIC (catalog number 26-4705) for $199.00
  • Model II Scripsit (catalog number 26-4530 and 26-4531) for $299.00 (later $399.00)
  • VisiCalc (catalog number 26-4511) for $299.00
  • Profile II (catalog number 26-4512) for $179.00

The Model 16 and Model 12

Radio Shack’s move into the business market was quite successful and profitable. It was frequently noted that the average Model II purchase (and accompanying software and peripherals) usually ended up costing around ten times more than the average Model I purchase. In 1980, Radio Shack established a leasing program for businesses to help them deal with the costs.

In January 1982, Radio Shack introduced the Model 16. The Model 16 was upwardly compatible with the Model II and could use Model II software, but also included a Motorola 68000 processor for running 16-bit programs. The Model 16 didn’t replace the Model II but served as a more powerful (and more expensive) alternative. For those who wanted to run Model 16 software on their Model II, Radio Shack sold the Model II to Model 16 Upgrade Kit (catalog number 26-6010) for $1499.00.

The Model II was discontinued in 1983 after Radio Shack introduced its replacement, the Model 12.

  1. The 1979 National Computer Conference ran from June 4th to 7th and the Model II was featured in both the main show and in the special Personal Computer Section. The 1979 show is best remembered for the introduction of VisiCalc on June 4. ↩︎

  2. Some sources claim the Model I name was unofficial, but that wasn’t the case. Radio Shack used the name Model I in their catalogs after the introduction of the Model II. ↩︎

  3. Radio Shack initially referred to the Model II (and Model I) without a definite article, for example, Model II instead of the Model II. They mostly abandoned that style by the time the Model III was introduced. ↩︎

  4. The IBM 5110 business computer, introduced in 1978, should not be confused with the IBM 5150, introduced in 1981 and better known as the IBM PC. ↩︎

Categories: Computers