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CoCo 3

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Looking for CoCo help? If you are trying to do something with your old Color Computer, read this quick reference. Want to contribute to this wiki? Be sure to read this first. This CoCo wiki project was started on October 29, 2004. --OS-9 Al

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This page was last updated on 08/31/2016. Total Pages: 650. Total Files: 937.


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Hooking Up the CoCo 3

The CoCo 3 is very similar to the original TRS-80 Color Computer in its capabilities. Most significantly for this section, they have the same connections to the outside world.

What's in the Case?

The CoCo 3 is a pretty simple computer as shipped. Inside they have a Motorola 68B09E microprocessor, 128K of dynamic RAM, and a built-in keyboard. A 512k RAM upgrade is available. On the right side is the expansion slot, where you can plug in Program PAKs (cartridges housing a program in a ROM chip), disk controllers, and other hardware expansions. On the back are DIN sockets for the serial port (often referred to as the "bit-banger"), the cassette port, and two joystick interfaces. There is also an RCA jack for the RF modulated audio/video output and a switch to select between channels 3 and 4 as well as a NTSC composite video output, an audio output, and a 10 pin connector on the bottom of the computer that is a 15khz RGB analog video output.

The only peripheral strictly necessary for interactive use of an unmodified Color Computer 3 is a television set. The television is the CoCo's video monitor, and the TV's speaker plays the sounds the CoCo produces. The CoCo's video signal is RF modulated, which just means that it is converted to a radio frequency signal so that it can be injected through the TV's antenna connector to the TV's tuner, which is designed to pick up a radio frequency signal. NTSC composite video is also available.

But all this conversion of the video signal to RF and back again degraded the signal and added noise to the picture. Don't expect a razor sharp display like what you're used to on your modern computer monitor. The CoCo 3 can also be plugged into the composite video input on a more modern TV and get an improved (though still far from perfect) picture. There is also a mono audio line out next to the video jack.

Another option to hook up a CoCo 3 to a modern TV is to convert the RGB analog output to HDMI using the circuit described in the project: CoCo 3 HDMI interface This will produce a much sharper picture and will allow you to use the 80 column text screen capabilities of the CoCo3, however, some games (not all) designed for the CoCo 1 or 2 will display in black and white when using the display in RGB mode. Many of these games do have patches available to allow them to display in color on a CoCo 3 RGB display however.