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Forum Index : Microcontroller and PC projects : For Grogster: The Atari 8-bit emulator for the Colour Maximite 2

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matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 12166
Posted: 12:18pm 09 Nov 2026
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An Atari 8-bit computer on the Colour Maximite 2

A new program in the 7.00.00RC4 programs zip. It runs on 7.00.00RC3 too; one pad's twin-stick play needs RC4.

https://github.com/UKTailwind/CMM2V1.5/releases/tag/v7.00.00RC4


Getting started
Copy the atari800 folder of CMM2_Programs_7.00.00RC4.zip to A:/atari800, then:

CHDIR "A:/atari800"
RUN "atari800.app"


It starts as an 800XL with 64K. F1 opens the emulator's own menu, where you load programs, disks, cartridges and tapes, and change the machine.


What it is
It is atari800 7.2.1, the Atari800 development team's emulator, with a new front end for the CMM2.

• The Atari 400 and 800, the XL and XE computers and the 5200 console, at the Atari's own 50 frames a second in MODE 7. On a G2 it leaves about two thirds of the processor spare.
• Programs (.xex), disk images (.atr and others), cartridges (.car, .rom), tapes (.cas) and BASIC programs.
• POKEY's sound, in mono or stereo.
• It passes Altirra's Acid800 test suite exactly as atari800 does on a PC, test for test.


The ROMs
AltirraOS and Altirra BASIC, Avery Lee's free replacements for Atari's operating system and BASIC, are built in, so it needs nothing else, and nearly all programs run with them.

Atari's own ROMs are not included. If you want them, copies are in the data folder of DnCraptor's atari800 repository on GitHub, https://github.com/DnCraptor/atari800: download and use them at your own risk. Put them in A:/atari800 before the first start and atari800 finds them by their contents, whatever their names.


BASIC
BASIC starts off, as atari800 has it, because most games load into the memory BASIC would use (on a real XL you hold OPTION for the same reason). Alt+B switches it on or off and restarts the Atari, and RUN "atari800.app", -basic starts with it on. Cartridges go in and out from Alt+C, without leaving the emulator.


The keys
F1             the menu
F2, F3, F4     OPTION, SELECT, START
F5             RESET (Shift+F5: switch off and on)
F6             HELP
F7, Pause      BREAK
F9             back to MMBasic (Ctrl+Alt+End too)
F12            turbo
Alt+B          BASIC on or off
Alt+R, D, C, T run a program, disks, cartridges, tapes
Alt+J          the joysticks and the mouse


What is printed on a key is what you get, following OPTION USBKEYBOARD. Caps Lock is the Atari's own CAPS key. Ctrl-C is an Atari key here.


Joysticks, paddles and the mouse
• The first USB gamepad is joystick 1, the second joystick 2. Any face button fires; Start, Select and L are START, SELECT and OPTION.
• With one pad, its right stick is joystick 2, for twin-stick games such as Robotron: 2084 (firmware RC4).
• The keypad is joystick 1 too.
• The mouse can be paddles, an ST or Amiga mouse, a trak-ball, a light pen or a Koala pad: Alt+J, Mouse device.


Tapes
A tape loads at once, as a disk does. To hear it load at the real 600 baud, turn off the SIO patch in the menu's Emulator Configuration.


Fixed on the way
atari800's patch of the operating system's tape routine was at the wrong address for the AltirraOS it ships with, so any use of a tape crashed the emulated Atari. That is corrected here.


Known problems
• At real tape speed, a tape with a program file after its boot loader stops with a checksum error under AltirraOS. With Atari's own operating system, or at the normal fast speed, it loads.
• It has been tried on a G2 only so far. Please report how it does on a G1.


Licences
atari800 is under the GNU GPL version 2 or later. Its source is github.com/atari800/atari800, with the CMM2's front end and changes in apps/atari800 of the firmware's repository. AltirraOS and Altirra BASIC are copyright Avery Lee, and may be copied and passed on with their notice.
Edited 2026-11-09 22:20 by matherp
 
al18
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Joined: 06/07/2019
Location: United States
Posts: 260
Posted: 02:43pm 09 Nov 2026
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It’s great seeing the Atari emulator ported.

I especially like the support for dual POKEY stereo emulation.

Can the emulation be switched between PAL and NTSC - the colors are different.

A great game that supports stereo sound and works in both PAL and NTSC is Fruity Pete https://www.atarimania.com/games/atari-400-800-xl-xe-games-fruity-pete-34018

The game is addictive, has 99 levels and a stereo soundtrack
 
matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 12166
Posted: 03:24pm 09 Nov 2026
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in the Atari app, press Alt+Y (System Settings) and set the video system to NTSC. F1, Save Configuration keeps that setting for next time. The picture stays the same size, and the game then runs at NTSC speed with NTSC colours.
 
Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 10099
Posted: 10:52pm 09 Nov 2026
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Dear GOD, Peter, how the hell did you do that SO FAST!!!!    

I am a little stunned......I only mentioned it yesterday.....  

I will try this out immediately.  

You must have been able to more-or-less just import the source code without that much work to have it going so soon!

What did you have to do, to port the code to the CMM2?
Smoke makes things work. When the smoke gets out, it stops!
 
Grogster

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Posted: 06:40am 10 Nov 2026
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SINGLE DISK images run fine, but MB(Multi-Boot) images crash the emulator.

Could it be filename length?
The Multi-Boot images have very long filenames(so I can include all the names of the games on that image), and the emulator on the CMM2 itself, moans that it cannot load the image file.

I will try renaming one of these to make it much shorter and let the thread know.

What has been done is AMAZING.

Sound is PERFECT.

My tinkering continues..........
Edited 2026-11-10 16:44 by Grogster
Smoke makes things work. When the smoke gets out, it stops!
 
Grogster

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Location: New Zealand
Posts: 10099
Posted: 07:15am 10 Nov 2026
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No, this port REALLY hates the Multi-Boot images.

I attach one here as a ZIP file - but just RENAME it to .ATR


MB-Boulderdash,Blue Max,Drelbs,Encounter.ZIP


Any attempt to load this ATR file - full file-name length or just as "MB.ATR", crashes the emulator.

I include this file for Peter to play with.  

With BASIC disabled in the emulator(same as holding OPTION down on the Atari), the result SHOULD be a simple menu, allowing you to select the game you want to boot.

The bugs not withstanding, I am really ASTOUNDED by this so far, Peter.....    
Smoke makes things work. When the smoke gets out, it stops!
 
Grogster

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Posted: 07:43am 10 Nov 2026
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Owwwwwwww - progress!!!!

VIDEO....
Smoke makes things work. When the smoke gets out, it stops!
 
matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 12166
Posted: 08:23am 10 Nov 2026
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Grogster, you need to uses the genuine roms downloaded from DrCraptor. Then your posted file works perfectly
 
Mixtel90

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Joined: 05/10/2019
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Posted: 08:32am 10 Nov 2026
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It's a pity there were major earthquakes in NZ while you were filming.  ;)

Very impressive! I used to go into a HiFi shop in Preston, where they started selling a few Atari machines from the back room. I remember that demo on an 800. :) The lad in charge of the computer side was always trying to sell me one, but they were pretty expensive machines - even the 400.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
 
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