[3] The initial goal of this project, called "Green Thumb", was to create a low cost videotex terminal for farmers, ranchers, and others in the agricultural industry.

[4][5] This terminal would connect to a phone line and an ordinary color television and allow the user access to near-real-time information useful to their day-to-day operations on the farm.

Motorola's MC6847 Video Display Generator (VDG) chip was released about the time the joint venture started.

An expansion connector was added to the right side of the case for future enhancements and ROM cartridges ("Program Paks").

On July 31, 1980, Tandy announced the TRS-80 Color Computer, which shares the same case, keyboard, and layout as the AgVision/VideoTex terminals.

Although the company's Ed Juge said in 1981 that the Color Computer was "our entry into the home-computer market", he described it as "for serious professionals", stating that a word processor and spreadsheet would soon be available.

The original version of the Color Computer sports a large silver-gray case with a calculator-like chiclet keyboard and was available with memory sizes of 4K (26-3001), 16K (26-3002), or 32K (26-3003).

Later versions removed the black keyboard surround and RAM button, and moved the TRS-80 nameplate to the mid-line of the case.

[1] The early CoCos only have eight RAM sockets, so upgrading to 32K requires piggybacking two sets of 4116 chips and adding a few jumper wires.

BYTE wrote in 1981 that through Extended Color BASIC, Radio Shack "has released the first truly easy-to-use and inexpensive system that generates full-color graphics".

In late 1982, a version of the Color Computer with a white case, called the TDP System 100, was distributed by RCA and sold through non-Tandy stores.

Peripherals included tape cassette storage, serial printers, a 5.25-inch floppy disk drive, a pen and graphics tablet called the X-Pad, speech and sound generators, and joysticks.

To cut production costs, the case was shortened by about 25% and a new, smaller power supply and motherboard were designed.

Aside from the new look and the deletion of the 12 volt power supply to the expansion connector, the computer was compatible with the previous generation.

Previous versions of the CoCo ROM were licensed from Microsoft, but Tandy could not convince them to provide further BASIC updates.

OS-9 uses memory-mapping (so each process has its own memory space up to 64K), windowed display, and a more extensive development environment that includes a copy of BASIC09.

Most of the improvements made it into NitrOS-9, a major rewrite of OS-9/6809 Level 2 for the CoCo 3 to take advantage of the features and speed of the Hitachi 6309 (if available).

[19] A joystick adapter designed by Steve Bjork increases the resolution of the joystick/mouse interface by a factor of ten at the expense of CPU time.

The core of the system is virtually identical to the reference design included in the Motorola MC6883 data sheet and consists of five LSI chips: The SAM is a multifunction device that performs the following functions: The SAM was designed to replace numerous small LS/TTL chips into one integrated package.

It can display 9 colors: black, green, yellow, blue, red, white, cyan, magenta, and orange.

CoCo enthusiasts created experimental programs to try to reverse engineer the modes, and were able to reconstruct the missing documentation.

On PAL televisions, instead of solid orange and blue, artifacts appear as vertical stripes of green and peach with soft edges and a width of almost four pixels.

The 6822 was eventually discontinued by Motorola, but was produced for Tandy as an application-specific integrated circuit with the part number SC67331P.

Wayne Green wrote in 80 Micro in December 1982 that Tandy had "virtually abandoned" the Color Computer.

Multi-Media One was introduced in July 1990, runs OS-9/68K on a 15 MHz Signetics 68070 processor with 3 MB RAM, and a 640×208 graphics resolution as well as supporting a 640×416 interlaced mode.

The Dragon 32 and 64 are British cousins of the CoCo based on a reference design from Motorola that was produced as an example of the capabilities of the MC6809E CPU when coupled with the MC6847 Video Display Generator and the MC6883 Synchronous Address Multiplexer.

The BIOS for the Dragon 32 was written based on specifications and API drawn up by Microsoft and, to a certain extent, PA Consulting of Cambridge.

It also featured a Centronics parallel port (not present on any CoCo), an integrated 6551A serial UART (on the Dragon 64), and a higher-quality keyboard.

In 1983, a version of the Dragon was licensed for manufacture for the North American market by Tano Corporation of New Orleans, Louisiana.

It is believed that Tandy blocked sales in the US with legal action due to copyright infringements on the ROM code.