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Unicorn Boards and Harmony Cart Menus - Single-chip 2600 Compatibility?

harmony cartridge unicorn board c101688-002 pre-production

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#26 atari2atari OFFLINE  

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Posted Fri Apr 13, 2012 9:32 AM

I just did - - no go! KOOL AID MAN on the native cartridge does not boot! Well, it does, but it just freezes on the opening title screen.

One of the difficulty switches is used for a pause feature on Kool Aide Man. When the switch is in the pause position on startup, the game freezes on the title screen. If you flip the switch, the game should start normally.

The difference that might appear on your console is the score display. On some consoles (like Thomas Chinese Jr.) the score digits overlap. This constantly triggers the collision detection which results in Kool Aide Man constantly bouncing back and forth in the top left corner of the screen. This makes the game unplayable.



Ah-ha! I will check again to see if the difficulty switch was flipped one way or another. That must be what it was - - I always thought the "freezing" in this game was the incompatibility bug! Good to hear that it's the score display, I'll check it and let you know.


Hmm, noted! I'd be interested in knowing more about your Chinese PAL Jr.!

On all (?) 2600 Jr. consoles (NTSC and PAL) that are made in China after late 1989 the signal timing in the TIA for the shifting pulses for the movable objects seems to be a little off from older versions of the TIA. Therefore when a game starts the shifting process in such a way that some of the shifting pulses happen during the visible part of the screen, the movable objects might be positioned slightly differently. This affects all PAL 7800 consoles too, BTW.

Something similar seems to be going on in your "unicorn" console too. You can see tis in your Pitfall II video. The game doesn't do an HMOVE in every line, so not all lines start with an eight pixel blank. Pitfall II tries to hide it with displaying a black eight pixel wide copy of missile 1 in those lines where it doesn't do an HMOVE. On your 2600 these missiles are shifted one pixel to the right. If you run Pitfall II in Stella and disable missile 1 with ALT-V, you can see that there are gaps in exactly the same scanlines where the one pixel shifts are in your video.

Other games worth testing for compatibility would be the starfield effect in Cosmic Ark, the tile screen in He-Man and the cobra head in G.I.Joe / Action Force.



Thank you, sir! That is all VERY helpful and informative!

I'll try those games and report back with compatibility.


Regarding the other side conversations on STELLA compatibility and TIA revisions, it's all very interesting, too.

It is strange to me that ATARI would be so short-sighted as to make revisions to the core of the ATARI 2600 system that broke the basic programming conventions that they initially had established!

-a2a

#27 Pioneer4x4 OFFLINE  

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Posted Fri Apr 13, 2012 10:05 AM

How many actual Atari branded games are affected by their changes? (If any)

#28 Thomas Jentzsch OFFLINE  

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Posted Fri Apr 13, 2012 3:04 PM

It is strange to me that ATARI would be so short-sighted as to make revisions to the core of the ATARI 2600 system that broke the basic programming conventions that they initially had established!

I don't think that they broken any conventions. Most old code I have seen so far, was very conservative.

Kool Aid Man is an exception. But, unlike in modern homebrews which tend to max out the hardware, IMO that's just the result of missing information. Or talent. :)

#29 atari2atari OFFLINE  

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Posted Fri Apr 13, 2012 9:59 PM

For anyone that is interested, I have posted a VERY lengthy thread in the "Hardware" section about built-in games on heavy and light sixers - -

http://www.atariage....lt-in-gamesrom/


It is somewhat relevant to this topic, since the "unicorn" also has a spot for a built-in ROM.


I would appreciate some of your wizardly advice over there, if you are willing . . . it could be quite a cool group project!


-a2a

#30 maiki OFFLINE  

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Posted Sat Apr 14, 2012 4:13 AM

Kool Aid Man is a bad game anyway. Not on my list...

#31 namedjughead OFFLINE  

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Posted Wed Feb 17, 2016 8:18 PM

Sorry for the necropost. atarti2atari can you post the schematics for the AV mod that you did on that 2600jr?

 

I have been looking for instructions to AV MOD my unicorn, but haven't had any luck. I'm pretty inexperienced with modding, so a schematic or guide would be very beneficial.

 

Thanks in advance.







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