Atari VCS/2600 - different TIA chip versions

[stonic]

I've found that Atari used least 5 different version of the TIA:

TIAs that show 2 sprites *
TIAs that show 3 sprites *
TIAs that have an issue with Wall Ball
TIAS that have an issue with Ebivision's Pac-Man and Pesco.
TIAs that have an issue with Kool-Aid Man, and Thunderground (Anteater is still unreleased, but should exhibit same issues as Kool-Aid Man and Thunderground).

* The "2 or 3 sprites" notes refer to a test program written by Bradfort Mott that was posted on Stellalist:
http://www.biglist.com/lists/stella/.../msg00028.html

The program shows either 2 or 3 sprites, depending on what TIA is used. This denotes a slight difference between the 2 most common TIA versions, although neither is a clear indication of any known incompatibility issues with any games.


There might also be a 6th variation that has issues with a few NTSC JRs, most PAL JRs, and all PAL 7800s that reveals a problem with PAL Centipede, and the 1987 re-release of Millipede. And then there's all the 3rd-party systems and adapters, of which I've done no testing on yet, so there's no telling what issues are waiting to be discovered there. I tried to interest a few VCS programmers to design a test program that would identify which version TIA they had in their systems. I figured, all they would have to do is create a display that uses all of the code tricks that are triggering the known issues. So you'd pop in the cart and immediately be able to tell which version TIA was in the system (ex: 3 of the 5 graphics displays are good, so it's TIA #3). I even contacted a few people who were working on mapping the TIA, but people either didn't respond or showed no interest. So for now the only other option is to try carts that are known to have issues with some TIAs with various systems. Once the list is more complete, the information could be incorporated into an emulator like Stella, as well as help homebrew programmers to make sure any tricks they use would be compatible across every variation.

Here is the DP FAQ: http://www.digitpress.com/faq/vcs_tia/vcs_tia.htm

[Steve W]

Wasn't the TIA in the 7800 designed by a clone maker who originally created it for the Coleco Gemini console? I remember hearing the Atari 7800 designers talk about that once.

[stonic]

Wasn't the TIA in the 7800 designed by a clone maker who originally created it for the Coleco Gemini console? I remember hearing the Atari 7800 designers talk about that once.

Never heard that before (do you have any links to that?). It's possible that was the case under Tramiel (sounds like something that penny-pincher would do..). If true, that should be the case with the 2600 "JR"s as well. Need to check more of those. However, I have 3 (1984) Rev A 7800s here - Two use an AMI and the other a Synertek, so that doesn't appear to have been the case originally. Atari should have had plenty of TIAs in stock by then, with at least 3 different chip manufacturers making TIAs for them, but who knows what happened after Tramiel took over. Whatever inventory Atari had of them might have been thrown out or sold off between 1984-86.

[Steve W]

It was in a presentation done by the creators of GCC about the founding of their company and the design of the Atari 7800. They're audio files and they were hosted on this site, but I can't seem to find any links to them now. They were interviews from (I believe) CGE 2003. Steve Wozniak, Jerry Lawson (Fairchild Channel F), the Blue Sky Rangers, Activision's and Imagic's founders were all there. The Digital Press site's been so chopped up I can't find it anymore.

[stonic]

The CGE keynotes are back online, in the 'scans and sights' section. The keynotes you mentioned were from CGE2K4, not CGE2K3, but there wasn't any GCC keynote.

[Night Driver]

Interesting. I never knew there were TIA variations.