Posts in the “Hardware” Category - page 8

The Mikrokolor Color Graphics Interface

The Mikrokolor was a color graphics interface for the TRS‑80 Model 100 that was sold by Andreasen’s Electronics Research & Development, Inc. The Mikrokolor hardware was designed by Paul Andreasen, the digital interface and graphics routines created by James Cole, and the software written by Andrew Baird. Andreasen’s Electronics Research & Development also sold versions of the Mikrokolor for the Model I, III, 4, and 12 and also the S-100 bus and the Apple II. There was also a $54.

The Archbold Speedup Board

The TRS‑80 Model I ran at a speed of 1.77 MHz. That speed was quite fast for a microcomputer at the time, but almost immediately people began designing speedup boards to increase it. The most famous of those speedup boards was the Archbold Speedup Board, designed by Bill Archbold and sold by Archbold Electronics.

The Archbold Speedup Board itself was a fairly small board (1.5" by 2.5").

The Holmes Internal Memory

Although the TRS‑80 Model I supported up to 48K of memory, there were only sockets for 16K within the Model I itself. The only official way to add more memory was to buy the Radio Shack Expansion Interface, which had sockets for an additional 32K of memory, for 48K in total. The Expansion Interface (without any memory) cost $299, making any kind of official memory expansion very expensive.

The other important feature of the Expansion Interface was the built-in floppy disk controller.

The Radio Shack “expansion box”

The TRS‑80 Model I was designed to allow for external expansion through what Steve Leininger described as an “expansion port” (the TRS‑80 card edge connector). Many people assumed that Radio Shack was developing a S-100 based expansion box to attach to the Model I. (The S-100 was a popular bus standard at the time.)

The first issue of the Radio Shack Microcomputer Newsletter in late 1977 contained a section answering some common questions about the new TRS‑80 computer.

The Micromint E-Z Color

Micromint sold several products for the TRS‑80 that were based on designs that Steve Ciarcia had presented in his Ciarcia’s Circuit Cellar column in Byte magazine. The Micromint E-Z Color was a color graphics interface for the TRS‑80 Model I and Model III that was based on his August 1982 column. In addition to the TRS‑80 version, there were also versions of the E-Z Color sold for the S-100 bus and the Apple II.

The Radio Shack Expansion Interface

The Radio Shack TRS‑80 Model I had few options for internal expansion other than adding a maximum of 16K of internal memory. The external expansion possibilities were reserved for a device Radio Shack called the Expansion Interface.

The Radio Shack Expansion Interface plugged into the back of the Model I using a six-inch long cable and was designed to serve as a base for the TRS‑80 monitor.


Probably the most popular of the TRS‑80 Model I and III color add-ons was the CHROMAtrs, introduced by South Shore Computer Concepts starting in 1982. It was available in several configurations:

a kit without case or power supply cost $99.00

a kit with case and power supply cost $129.00

a fully-assembled and tested unit cost $169.00

Each CHROMAtrs unit supported both the Model I or Model III and would work with either computer using the proper cable.

The Percom Separator

The Radio Shack Expansion Interface added single-density floppy disk support to the TRS‑80 Model I. Floppy disks were a great improvement over cassettes. But many people reported problems with reliability, particularly when reading or writing lower disk tracks. CRC errors and locked out tracks occurred with disturbing regularity.

The Separator, sold by Percom for $29.95, fixed all of those problems.

The Electric Crayon

Back in the late 1970’s, the Apple II and the TRS‑80 Model I were fierce competitors for computer sales. One advantage the Apple II had over the Model I was the ability to display color graphics. One of the first Model I productsto address this deficiency was the Percom Electric Crayon. Percom introduced the Electric Crayon in December 1979 for a base price of $249.00. It was featured on the cover of the January 1981 issue of 80 Microcomputing.

Mikeegraphic Graphic System

The Mikeegraphic Graphics System was a high-resolution graphics add-on for the TRS‑80 Model I and Model III. It was sold by Mikee Electronics Corporation for $340. Originally known as the Mikeeangelo when it was introduced in late 1981, the name was changed to Mikeegraphic just a few months later, presumably to avoid confusion with another product.