R_Leo_1 Posted October 1, 2019 Share Posted October 1, 2019 I haven't had any issues with the 2600 incompatibilities on the 7800 so far, but I've recently been wanting to play Kool-Aid Man and was wondering if you could replace the TIA in the 7800 with an earlier one, to possibly fix some of the compatibility issues. Thanks Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 1, 2019 Share Posted October 1, 2019 Kool Aid man has worked for me on pretty much all 7800s I've tested it with. Now, you do have to make sure you have the difficulty switches in the correct position or else the game will start up in PAUSE mode making it appear that it is locked up or not working at first. But to answer your question, if you should happen to find that Kool Aid main has the overlapping score digits, then you should be able to replace the TIA with any from a 4 switch/6 switch variant. But again, I've only seen that issue on one Jr. that I had sometime back. Biggest offender of compatibility with 2600 games is the extra timing circuit that was added in to the later model 7800s. I just de-solder the right leg of C64 and call it a day. 2 Quote Link to comment Share on other sites More sharing options...
R_Leo_1 Posted October 1, 2019 Author Share Posted October 1, 2019 8 minutes ago, -^CrossBow^- said: Kool Aid man has worked for me on pretty much all 7800s I've tested it with. Now, you do have to make sure you have the difficulty switches in the correct position or else the game will start up in PAUSE mode making it appear that it is locked up or not working at first. But to answer your question, if you should happen to find that Kool Aid main has the overlapping score digits, then you should be able to replace the TIA with any from a 4 switch/6 switch variant. But again, I've only seen that issue on one Jr. that I had sometime back. Biggest offender of compatibility with 2600 games is the extra timing circuit that was added in to the later model 7800s. I just de-solder the right leg of C64 and call it a day. Oh okay, thanks for the info! I wasn't aware that it worked on most units, I'll have to snag a copy to test out on my 7800. Quote Link to comment Share on other sites More sharing options...
Tempest Posted October 1, 2019 Share Posted October 1, 2019 Why did Atari decided to add an entire circuit to the 7800 to fix one game? I suppose they didn't do much testing so they didn't know it was going to break other games, but that seems like an awful lot of extra expense to fix one game. Especially since it wasn't exactly a major release or anything. Did they think other games would also have the same problem? Quote Link to comment Share on other sites More sharing options...
R_Leo_1 Posted October 1, 2019 Author Share Posted October 1, 2019 Since Dark Chambers released for both systems at around the same time, it may have just been the most relevant incompatibility for them to fix at the time, however, I agree that it seems unnecessary, given it's just one game. 1 Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 1, 2019 Share Posted October 1, 2019 4 minutes ago, Tempest said: Why did Atari decided to add an entire circuit to the 7800 to fix one game? I suppose they didn't do much testing so they didn't know it was going to break other games, but that seems like an awful lot of extra expense to fix one game. Especially since it wasn't exactly a major release or anything. Did they think other games would also have the same problem? I'm not totally sure on that. I've always thought it must affect more games, but the actual '84 made 100% compatible 7800s do NOT include this extra timing circuit and get this... they still play 2600 dark chambers also! Both my original 7800 (With Eckart's DevOS mod on it), and my daily driver 7800 are both 100% compatible and do not have that circuit on their layout. I've also seen 7800s that have the circuit in the silkscreen on the board, but not populated at all?! So who can say. It is just one of a 1000 reasons why it has been a challenge to create new hardware add-ons and flash carts for the 7800 due to all the different hardware revisions. I've always clipped C64 when I find it because many of the advance 2600 programming tricks like Darrel Spice's demos do NOT work on the 7800 with that circuit in place. @Shawn can attest that his 7800 wouldn't play the Arkyology proto until he clipped c64 out of circuit. So it seems to me it is best to remove the circuit since I only know of just 2600 dark chambers being affected by it. This is a classic case of the needs of the many totally outweighs the need of the one. 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted October 1, 2019 Share Posted October 1, 2019 32 minutes ago, Tempest said: Why did Atari decided to add an entire circuit to the 7800 to fix one game? Remember, Atari, Inc. (Warner-era) itself did not design the 7800 initially. It was a GCC project, along with many of the latter-era 2600 titles that look and play so much better than the early games. I’d bet a lot that when DARK CHAMBERS was released, Atari Corp. (Tramiel-era, post July 1984) did this “fix” in-house rather than ask GCC to do full compatibility testing and engineering analysis for any fix necessary. Oh course I don’t know this to be fact, but it’s a reasonable supposition given how quick-and-dirty Tramiel’s companies always did engineering over the years, first at Commodore and then later Atari Corp. 2 Quote Link to comment Share on other sites More sharing options...
Tempest Posted October 1, 2019 Share Posted October 1, 2019 G=that's what's confusing. Given how tight fisted Atari was with money at the time, it boggles my mind that they decided to go through all the extra expense to engineer and add this circuit to fix one game. I can only assume they thought that future games would also have this problem. That being said, why does the original 84 Atari 7800 play Dark Chambers correctly? I wonder if there's a way to fix other 7800's to play it AND disable that circuit to fix other games? Probably no worth exploring as DC is only so-so on the 2600 anyway (although I enjoyed it back in the day). Quote Link to comment Share on other sites More sharing options...
+Mitch Posted October 1, 2019 Share Posted October 1, 2019 Defender 2 also has issues in addition to Dark Chambers. Mitch Quote Link to comment Share on other sites More sharing options...
Tempest Posted October 1, 2019 Share Posted October 1, 2019 Just now, Mitch said: Defender 2 also has issues in addition to Dark Chambers. Mitch Ah I forgot about that. Can the roms be hacked to work correctly or does it require a hardware fix? Quote Link to comment Share on other sites More sharing options...
+Mitch Posted October 1, 2019 Share Posted October 1, 2019 It is the extra on board RAM chip that causes the problem. I don't know if you can patch around that. Mitch Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted October 1, 2019 Share Posted October 1, 2019 18 minutes ago, Mitch said: Defender 2 also has issues in addition to Dark Chambers. Mitch I don’t actually have 2600 DARK CHAMBERS to try with my 7800s, but I do have STARGATE (aka DEFENDER II). I need to give it a try later today. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 1, 2019 Share Posted October 1, 2019 I also have Stargate and I wasn't aware of this. Too bad since Stargate is actually a really excellent game! Now what is possible is that several of the troublesome games like the Activision games that start working when you disable the extra circuit do have working version roms on unmodded hardware through the harmony and Encore. But things like the Parrot demo and other advanced color display tricks do NOT like this circuit in place. I'd imagine it might cause problems with some homebrews but I've not tested that. Atari doesn't make any sense on what revisions were done either. I'm working on a 7800 right now that says it was made in May of 1987 and it has the expansion port physically on it. But it also has the extra timing circuit installed in place and does NOT have chips in sockets. All the ICs are soldered directly to the mainboard. So it would seem that even in the 87 revision 7800s, Atari was still adding in the expansion port for who knows what reason. And yes, this 7800 also has the bottom shell to expose the port. The revisions are really all over the place and in the case of the 7800 I'm convinced that Atari just threw together whatever they had laying around to kick them out the door mixing and matching without any real system in place to track these "revisions". 1 Quote Link to comment Share on other sites More sharing options...
Tempest Posted October 1, 2019 Share Posted October 1, 2019 10 minutes ago, -^CrossBow^- said: The revisions are really all over the place and in the case of the 7800 I'm convinced that Atari just threw together whatever they had laying around to kick them out the door mixing and matching without any real system in place to track these "revisions". That's probably exactly what happened. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted October 1, 2019 Share Posted October 1, 2019 For what it's worth, I just played several games of STARGATE on my daily-driver 7800 without a problem - it's a typical silver-label Atari Corp. label cartridge, and the system is an A1-serial number unit (with the expansion interface as well). Quote Link to comment Share on other sites More sharing options...
Tempest Posted October 1, 2019 Share Posted October 1, 2019 When I get my 7800 back (the afore mentioned hodgepodge system), I'll try Stargate and see if it works. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 2, 2019 Share Posted October 2, 2019 Actually Tempest... I was going to wait and surprise you. As you know I disabled C64 from circuit on yours. Well, I just tested Stargate and it works 100% without issues from what I could tell. Your 7800 is quite unique to be honest. It literally is a mix of '84 design in a later rev mainboard. Space Shuttle is working now as well, but Decathlon is still a no go on your 7800. Honestly even my daily driver 7800 has issues getting that game to work. Track n Field is better anyway hehe. But I do know that Decathlon from a Harmony does work so you can always go that route on this 7800 if you really wanted to play that game and kill a few controllers in the process. 1 Quote Link to comment Share on other sites More sharing options...
+Mitch Posted October 2, 2019 Share Posted October 2, 2019 I seem to remember that Stargate/Defender 2 doesn't always crash but just has some graphically issues. Like the starfield being missing on the opening screen. It has been quite a few years since I did my testing though. Mitch Quote Link to comment Share on other sites More sharing options...
Tempest Posted October 2, 2019 Share Posted October 2, 2019 1 hour ago, -^CrossBow^- said: But I do know that Decathlon from a Harmony does work so you can always go that route on this 7800 if you really wanted to play that game and kill a few controllers in the process. I'm going to use my Harmony cart so it won't be a problem. I guess it's just DC then. I wonder if someone fixed that one? Wasn't it a weird instruction that was the cause (something with initializing Ram?) Quote Link to comment Share on other sites More sharing options...
+Mitch Posted October 2, 2019 Share Posted October 2, 2019 I think if you use the version with F8 banking instead of FE banking it works fine on all 7800s. Mitch Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 2, 2019 Share Posted October 2, 2019 52 minutes ago, Mitch said: I think if you use the version with F8 banking instead of FE banking it works fine on all 7800s. Mitch But that is a rom hack version of the game correct? I still find it odd that Space Shuttle, Robot Tank, and others that should be problematic...aren't. But then Decathlon... Tempest's 7800 does another interesting trick with C64 removed from circuit but I will wait on that one. Quote Link to comment Share on other sites More sharing options...
+Mitch Posted October 2, 2019 Share Posted October 2, 2019 I thought the blue label rerelease used F8 banking. Mitch Quote Link to comment Share on other sites More sharing options...
Tempest Posted October 2, 2019 Share Posted October 2, 2019 3 hours ago, -^CrossBow^- said: Tempest's 7800 does another interesting trick with C64 removed from circuit but I will wait on that one. Oh? Now I'm curious. Quote Link to comment Share on other sites More sharing options...
Trebor Posted October 2, 2019 Share Posted October 2, 2019 Batari provided a detailed write-up concerning the circuit a little over a decade ago while troubleshooting Harmony compatibility. It's worth the read. Regardless, -^CrossBow^- piqued my curiosity too. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted October 3, 2019 Share Posted October 3, 2019 1 hour ago, Trebor said: Batari provided a detailed write-up concerning the circuit a little over a decade ago while troubleshooting Harmony compatibility. It's worth the read. Regardless, -^CrossBow^- piqued my curiosity too. So I've never really paid this timing circuit business all that much attention. Where about is C64? I can't find it on my 7800 board photos. The linked thread has a little schematic put together by Fred that refers to the 74LS02. However, my 7800's have a 74LS3 and a 74LS08, along with a couple others. Presumably it's one of those chips? Quote Link to comment Share on other sites More sharing options...
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