Color Computer 3 (NTSC)
Color Computer 3 (NTSC)



Setname:  coco3   
Year: 1986
Manufacturer: Tandy Radio Shack
Status: good  works
Type: Home Computer
Parent: Color Computer
Emulation info
Overall emulation:  good   
Color emulation:  good  
Sound emulation:  good  
Graphics emulation:  good  
Savestates:  unsupported   

Tech info
 Base hardware: (available in all slot configurations)
M6809E ("maincpu")cpu 3579545 Hz
Speaker ("mono")audio
DAC ("dac")audio
Wave ("wave")audio
Screen ("composite")raster horizontal 640 x 240 @ 60.000000
Screen ("rgb")raster horizontal 640 x 240 @ 60.000000
Media devices
cassette ("cassette") cassette cass wav, cas
cartridge ("ext") cartridge cart ccc, rom
harddisk ("vhd0") harddisk1 hard1 vhd
harddisk ("vhd1") harddisk2 hard2 vhd
RAM options
128K 131072
512K 524288
2M 2097152
8M 8388608
Software lists

 Optional hardware: (available with specific slot configurations)

 Configure the slot options for coco3:
 Slot Value

Show detailed info about 'Configurations' of this system

Right Controller Port (P1) Unconnected
 The Rat Graphics Mouse
 Diecom Light Gun Adaptor
Left Controller Port (P2) Unconnected
 The Rat Graphics Mouse
 Diecom Light Gun Adaptor
Hi-Res Joystick Interfaces None
 Hi-Res in Right Port
 Hi-Res CoCoMax 3 Style in Right Port
 Hi-Res in Left Port
 Hi-Res CoCoMax 3 Style in Left Port
Cart Auto-Start Off
Real Time Clock Disto
Becker Port Off
Drivewire Server TCP Port 65500
RX Baud 110
Start Bits 0
Data Bits 5
Parity None
Stop Bits 0
Artifacting Off

Show detailed info about 'Slot Options' of this system
Slot options

NameValueCompatible device(s)
ext banked_16kcocopak_banked
 fdcv11 coco_fdc_v11
rs232 keyboardserial_keyboard
 printer serial_printer

Romset info
ROM NameSizeCRC32SHA1Dump StateBIOS option
coco3.rom32768 b4c88d6ce0d82953fb6fd03768604933df1ce8bc51fc427dgood


* CPU: Motorola 68b09e (uses an external clock generator) 2 MHz (0.89MHz under RS-DOS for compatibility with FD expansion unit)
* RAM: 128 KB (up to 512 KB. There were 1MB and 2MB upgrade boards as well)
* ROM: 32 KB
* Text Modes: 32 x 16, 40 x 25, 80 x 25
* Graphic Modes: Several graphic modes, the most interesting were: 320 x 200 (16 col.), 640 x 200 (4 col.), 640 x 400 (4 col. if 512 KB RAM)
* Colors: 64
* I/O Ports: Tape, Composite Video, analog RGB connector for use with Tandy CM-8 monitor, 2 joystick ports, cartridge slot, RS232
* Keyboard: Full-stroke keyboard
* OS: with optional disk drive : RS-DOS, OS-9 Level 2 was also popular
* Built In Language: Tandy Extended Color Basic


MESS supports three different systems

* coco3 [Tandy Radio Shack Color Computer 3 (NTSC)]
* coco3p [Tandy Radio Shack Color Computer 3 (PAL)]
* coco3h [Tandy Radio Shack Color Computer 3 (NTSC; HD6309)] - the MPU has been replaced by a Hitachi 6309, notice that this chip has extra features not documented by Hitachi

For each driver, MESS supports the following devices

- a "cartridge" (cart), for .ccc and .rom files
- a "cassette" (cass), for tapes in .wav and .cas format
- a "harddisk" (hd), for .vhd files
- up to four floppy drives, "floppydisk0" (flop0) to "floppydisk3" (flop3), for disk images in one of the following formats: .dsk, .os9, .vdk and .dmk

Also a "snapshot" (dump) feature is available for .pak files and a "quickload" (quik) feature is available for .bin files.

Finally, the "printer" (prin) is emulated as well.

Real Time Clock

MESS contains two different real time clocks: Disto and Cloud-9. Currently they can be set under the "DIP Switches".

* Disto Real Time Clock
* Chip: OKI m6242B
* Addressed: $FF50 and $FF51
* Cloud-9 Real Time Clock
* Chip: Dallas Semiconductor's Phantom Time Chip DS1315
* Addressed: $FF79, $FF78, $FF7C


Read the entry for the Color Computer and Color Computer 2 drivers. Much of the information there also applies to this driver.

MESS emulation also contains an implementation of Jeff Vavasours' Virtual Hard Disk. See his Color Computer 3 emulator for information regarding it.


These systems require full keyboard emulation to work correctly. At startup, full keyboard emulation mode is enabled by default. Whilst in full keyboard emulation mode, some key associated functionality may be disabled (like the ESC key for EXIT). The keyboard emulation mode is toggled using the "Scroll Lock" key (by default).

Original Keyboard: QWERTY Full-stroke keyboard,

1! 2" 3# 4$ 5% 6& 7' 8( 9) 0 :* -= BREAK


CTRL A S D F G H J K L ;+ ENTER Left Right

SHIFT Z X C V B N M ,< .> /? SHIFT Down


RAM options

Different RAM configurations are possible for these drivers in MESS. You can switch between them, changing the -ramsize parameter. At command line, you simply have to add ''-ramsize ram_value'', where //ram_value// can assume one of the following values

512k (default)

History and Trivia

The Tandy Color Computer 3 is the successor of the Tandy/TRS-80 Color Computer 2.

The CoCo3 came with 128K RAM, an analog RGB video port, enhanced 640x192 graphics capability, a 64-color palette and much more. (All ports contained on the CoCo 1 and 2 models were also available on the CoCo3, e.g. RS-232 serial, cassette, right and left joystick and a 40-pin expansion slot.)

The CoCo3 was upgradeable to 512 KB RAM. (After-market RAM upgrades have gone as high as 8MB, with rumors that 16MB and 32MB RAM upgrades may also be possible). A Multi-Pak (a 4-port bus expander) plugged into the Expansion Slot allowed use of controllers for floppy disk drives, hard drives (MFM, RLL, SCSI and now even IDE), multi-port true RS-232 devices, MIDI units and much much more.

It can work with OS-9 Level II (an operating system designed for 6809 processors).

As its microprocessor was still an 8 bit (strange choice when Atari and Commodore were using a 68000), it couldn't access simultaneously to the 128k (or 512k), and thus used several RAM banks which could be switched (as the Thomson TO8, or MSX 2 computers). Unlike the CoCo and CoCo II the 3 had an interrupt controller. This did away with a lot of the timing loops used in its predecessors, and actually took some of the fun out of programming in Machine Language.

Tandy made several prototypes of a Color Computer model IV but it was never released.

(info from


* CoCo Quest Color Computer Games and More! --
* Sock Master's Web Page --
* --
* CoCo 3 at --

Other Emulators

* CoCo III Emu by Jeff Vavasour --

Edit the History info for this game.


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