2600 home brew compatibility on 7800?

[Jase]

Hi - I just took delivery of 2 7800 home brews and 6 for the 2600, along with the fantastic Atarivox, and I’m really amazed with the quality of the games and their presentation! It’s like being in the 80s again, buying new games for the old VCS!

My usual choice is to play on my 7800, but I found that Space Rocks, Star Castle and Scramble won’t boot. They work fine on my 2600jr though.

Anyone know why? My 7800 is a PAL version.

TIA

[+Gemintronic]

I've never had any compatibility problems with the 2600 games I've made.  In fact, my first hardware tests usually start on a 7800.

 

Once a client / collaborator had a 7800 that corrupted the high res title screen slightly.  Couldn't reproduce on other known good 7800s.

[+DrVenkman]

29 minutes ago, Jase said:

My usual choice is to play on my 7800, but I found that Space Rocks, Star Castle and Scramble won’t boot.

Weird. I think those are all Melody board-based cartridges. Do you have a Harmony Cart? If so, I bet it also doesn’t work. Of those, I only own Space Rocks but it, and my Harmony Cart (also Melody-based), both work great on both of my 7800’s. 

 

Might be a power issue - what kind of PSU are you using on your 7800? Are you comfortable opening it up to measure the output of the internal voltage regulator with one of those problematic titles running? (Or at least plugged in with the console turned on)?

 

 

[Jase]

41 minutes ago, DrVenkman said:

Weird. I think those are all Melody board-based cartridges. Do you have a Harmony Cart? If so, I bet it also doesn’t work. Of those, I only own Space Rocks but it, and my Harmony Cart (also Melody-based), both work great on both of my 7800’s. 

 

Might be a power issue - what kind of PSU are you using on your 7800? Are you comfortable opening it up to measure the output of the internal voltage regulator with one of those problematic titles running? (Or at least plugged in with the console turned on)?

 

 

Yes I have a harmony cart and it works fine!?

The power supply is the original Atari one. I have no problems opening up the 7800, I fitted an A/V mod to it. I’ll have a look and see.

What happens is it just boots to the internal game, Asteroids. It’s as if there isn’t a cart plugged in. I’ve checked and checked that they are plugged in correctly. Very strange!

[Albert]

Of those three games, Space Rocks and Scramble use a Melody board, and Star Castle Arcade uses our Aria board.  Unfortunately, sometimes there are compatibility issues with some 7800 systems, and we tend to call these systems "evil 7800s".  Atari tweaked the 7800 several times during its run, trying to fix compatibility issues with 2600 games, but it seems they'd fix one issue only to introduce others.  Even some of Atari's own games have issues on the 7800, and some third-party cart have issues as well. 

 

I'm sorry you've had issues with these three games.  I would be glad to replace them, but it's likely the replacements would also not work on that particular 7800. 

 

 ..Al

[Jase]

Hi Al - thanks for the reply! Yes I’ve read about these rogue 7800’s, I was guessing maybe mine was one of them!

As for the replacements, thanks for the offer but it’s fine! I do actually like to run 2600 games on a 2600, mainly to impress friends on the new innovations from you guys, but also for the sheer fun of it. 
By the way, my only regret with my order is that I didn’t order them all to be boxed. I’m so impressed with the Galaga and WoW boxes that I’d like to be able to have them for the remaining 6 carts! Is there a way I could do this, do you offer these as a separate item? I’ll likely order one or two other carts at the same time to make it worth your while!

And finally, thank you so much for this amazing site! It truly is a superb experience buying new games for my old Atari’s, and they are all incredible!

Cheers

Jase

[Albert]

Just now, Jase said:

Hi Al - thanks for the reply! Yes I’ve read about these rogue 7800’s, I was guessing maybe mine was one of them!

I have a bunch of 7800s (which I use to demo games at shows), and of those one is a straight out "evil" 7800, and then I have another that's about halfway between normal and evil (runs nearly everything, but sometime I run into a game that won't run).  It's really annoying that they exist!

Just now, Jase said:

As for the replacements, thanks for the offer but it’s fine! I do actually like to run 2600 games on a 2600, mainly to impress friends on the new innovations from you guys, but also for the sheer fun of it.

Glad you have a 2600 you can use to enjoy the games. 

Just now, Jase said:

By the way, my only regret with my order is that I didn’t order them all to be boxed. I’m so impressed with the Galaga and WoW boxes that I’d like to be able to have them for the remaining 6 carts! Is there a way I could do this, do you offer these as a separate item? I’ll likely order one or two other carts at the same time to make it worth your while!

Yes, I'd be glad to sell you the boxes separately for any games you previously purchased without boxes.

Just now, Jase said:

And finally, thank you so much for this amazing site! It truly is a superb experience buying new games for my old Atari’s, and they are all incredible!

Thanks for the kind words, glad you're enjoying the site!

 

 ..Al

[+-^CrossBow^-]

He stated he has a PAL 7800...do we know if the PAL units feature the extra timing circuit that was introduced on the mid made 7800s? Be curious if it does exist and if something similar to our removing C64 from circuit might be something similar needed here on PAL units?

 

[Jase]

26 minutes ago, -^CrossBow^- said:

He stated he has a PAL 7800...do we know if the PAL units feature the extra timing circuit that was introduced on the mid made 7800s? Be curious if it does exist and if something similar to our removing C64 from circuit might be something similar needed here on PAL units?

 

That’s interesting! Would be cool if there is a mod...

[AtariLeaf]

I was playing some of my 2600 homebrews on my 7800 and of the six I played, Ladybug was the only one that didn't work on this particular 7800, just a black screen, but it works fine on other 7800s and of course my 2600s. I don't know which revision this evil 7800 is but it has no expansion slot. 

 

 

[socrates63]

I recently tried Space Rocks on my 7800 and it wouldn’t work. I then read that some 7800 may run into compatibility issues as mentioned in this thread. I’ve always wanted a 6 switcher and it should arrive in a few days — problem solved (hopefully)

[+-^CrossBow^-]

11 hours ago, socrates63 said:

I recently tried Space Rocks on my 7800 and it wouldn’t work. I then read that some 7800 may run into compatibility issues as mentioned in this thread. I’ve always wanted a 6 switcher and it should arrive in a few days — problem solved (hopefully)

I've stated this before and I will state it once again. Your 7800 likely has the extra timing circuit in it and that can cause issues with some of the homebrews. Clipping one of the legs on C64 in the right center of the mainboard will disable that part of the circuit and restore compatibility with those games from my testing. So if you feel like giving it a shot, you could open up your 7800 and look to see if that capacitor is present. It usually likes like a resistor but it is in fact a ceramic banded capacitor.

 

[SearsRoebuck]

Uh oh, this gives me pause. Crossbow, since you've had my 7800 at your place twice now, I hope my 7800 fell before the 'evil' range? I ask this because I am about to start getting alot of 2600 homebrew in the coming months, which previously I only had 1-2 of. IIRC Star Castle is the only homebrew I have run on that system. I can't remember what you tested on it. 

[+-^CrossBow^-]

7 hours ago, SearsRoebuck said:

Uh oh, this gives me pause. Crossbow, since you've had my 7800 at your place twice now, I hope my 7800 fell before the 'evil' range? I ask this because I am about to start getting alot of 2600 homebrew in the coming months, which previously I only had 1-2 of. IIRC Star Castle is the only homebrew I have run on that system. I can't remember what you tested on it. 

I'm sure I tested the parrot bus stuffing demo on it as that is a standard test I run. I've only seen the bus stuffing demos fail on the 7800s with the extra timing circuit in them for 2600 Dark Chambers. Let me check the pics on your 7800 in my records and see if the circuit was present and if I disabled it (This is the one mod I tend to do without asking my clients since it is much more beneficial than not).

 

You should be in the clear on yours. You have an older '84 era revision main board with the expansion port and the extra timing circuit isn't present or even silkscreened on your 7800 mainboard. Your 7800 appears to have been made sometime in the 37th week of 1986 BTW although your NCR made CPU in your 7800 is from early 1984. I also see that I tested your 7800 with 2600 Decathlon and it worked without issue so I think you should be good on 2600 homebrews.

 

[socrates63]

On 7/6/2020 at 9:26 AM, -^CrossBow^- said:

I've stated this before and I will state it once again. Your 7800 likely has the extra timing circuit in it and that can cause issues with some of the homebrews. Clipping one of the legs on C64 in the right center of the mainboard will disable that part of the circuit and restore compatibility with those games from my testing. So if you feel like giving it a shot, you could open up your 7800 and look to see if that capacitor is present. It usually likes like a resistor but it is in fact a ceramic banded capacitor.

 

Thanks for the info. I found the bin file for Space Rocks and just loaded it this morning via Harmony Encore -- an amazing game. I'll look into the solution you mentioned.

[+-^CrossBow^-]

32 minutes ago, socrates63 said:

Thanks for the info. I found the bin file for Space Rocks and just loaded it this morning via Harmony Encore -- an amazing game. I'll look into the solution you mentioned.

Yes I should have mentioned that I believe some of these troublesome homebrews and other games tend to work through the Harmony. Either the extra delay in loading up the games from the Harmony is what makes them work or there is something on the Harmony to address it. Batari could tell us more on those specifics. Unless the roms themselves were made to work?

 

Also that circuit isn't on every 7800. I'm not sure when it was first implemented, but I'd guess around '87 and then it would seem that in the later years of the 7800 it was removed again? I've found 7800s with the components silkscreened on the board to have it, but not actually be populated. There are older revisions that don't even have the circuit in mind since there isn't any space or silkscreening for it, and I've seen newer systems that have the silkscreening but again the components not populated. I think I had a late '88 made unit that came that way.

 

But if it is present you will find it where I stated.

 

[nadir]

I've got a 7800 that was purchased very late, but don't know the build date.  Is there a serial number to date conversion list somewhere?

 

Anyways, it had C64, but after clipping it I've yet to find any game so far that won't run.  I don't have any homebrew yet (I have 2 on order right now, I'd imagine they'll be in a batch going out in the next couple of weeks), but I've got a number of the other troublesome ones (Robot Tank, Supercharger, etc).

[AtariLeaf]

Maybe I'm weird this way but I prefer using a 2600 to play 2600 games and keep my 7800 for 7800 games. 

 

I understand perhaps some don't have a 2600 or perhaps space limits them to the one console but to me a 2600 isn't prohibitively expensive to rule one out.

 

Personally I don't like the washed out/muted way a 7800 makes the colors of many 2600 games look anyway which makes any 7800 a non starter for me as a daily driver of 2600 games.

 

Hell I've had ladybug for a dozen years and only last weekend discovered it didnt work on my main 7800. That's how little I play 2600 games on it

[+-^CrossBow^-]

55 minutes ago, nadir said:

I've got a 7800 that was purchased very late, but don't know the build date.  Is there a serial number to date conversion list somewhere?

 

Anyways, it had C64, but after clipping it I've yet to find any game so far that won't run.  I don't have any homebrew yet (I have 2 on order right now, I'd imagine they'll be in a batch going out in the next couple of weeks), but I've got a number of the other troublesome ones (Robot Tank, Supercharger, etc).

The only game I've found that I can confirm is usually...note I said usually affected by this is the 2600 version of Dark Chambers. But when I was putting a UAV into Tempest's 7800 last year I think? It did have the extra timing circuit so I clipped C64 and yet his 7800 which didn't run the bus stuffing demos before now could, and...yeap. 2600 Dark Chambers still worked on his. So you just never know it that game will be effected or not. But if I want to play Dark Chambers, I'm playing the 7800 version over the 2600 version anyway. It has been stated that Stargate and I think Secret Quest could also be affected and no longer work if you disable the circuit but I've not seen this be the case myself.

 

As for how to know when a system was manufactured? That is more complicated than it really should be. You can get an idea on when it was at least packaged and sent to be sold at retailers based on Serial #s. But to actually know you have to pop it open and start looking at date codes on the chips along with the revision of the mainboard you have. But usually the date codes on the chips will get you a better idea of about when it was actually made. The latest date you find on a chip, you know the system was made that week or a little after. I knew the details about @SearsRoebuck's 7800 because I photo an document all the consoles I work on. I use it as a reference if a client has questions about something or any possible issues that might come up. In this case I pulled up the pic of his 7800 main board and I could read the date stamps on most of the chips in the pictures I took along with being able to see the board layout and whether he had the extra timing circuit or not.

 

[nadir]

57 minutes ago, AtariLeaf said:

Maybe I'm weird this way but I prefer using a 2600 to play 2600 games and keep my 7800 for 7800 games. 

 

I understand perhaps some don't have a 2600 or perhaps space limits them to the one console but to me a 2600 isn't prohibitively expensive to rule one out.

My 2600 went up in smoke a number of years ago and all I currently have left is a 7800, so that's what I use for everything as so far it's working for everything.  ?

[+DrVenkman]

58 minutes ago, nadir said:

I've got a 7800 that was purchased very late, but don't know the build date.  Is there a serial number to date conversion list somewhere?

The prefixes on the bottom case serial number sticker is the first thing to check, assuming it's an original case bottom. The first ~5,000 or so pilot production units were assembled in Atari's El Paso facility; they have EP prefixes on the serial number sticker. The next batches were made in 1984 and 1985. They have AT-84 and AT-85 prefixes. Then there are basically "all the rest" which have mostly A1 prefixes. By far these seem to be the most common. I think the last batch had "X" or maybe "AX" though I've never seen one personally. The problem with this method though is that there's no guarantee on it - my player 7800 had a shattered bottom case when I got it. A friend sent me a replacement from a busted up unit of his. The original serial number on mine was an A1 prefix but the replacement is AT-84. 

 

The second thing you can do is open it up and check the latest date code you can find on the chips, especially if the chip is soldered and there's no sign it has been replaced. That will give you the absolute earliest it could have been assembled. You can also check for the presence of absence of the timing circuit capacitor, the revision of the PCB, etc.

 

But the problem with all of this is 7800 assembly was kind of all over the place - Atari used whatever parts were on hand when they assembled these after the first couple years, it seems like, mixing up board revision, cases with or without cutouts for the Expansion interface, which may or may not be present on the PCB, etc. 

 

[nadir]

16 minutes ago, -^CrossBow^- said:

It has been stated that Stargate and I think Secret Quest could also be affected and no longer work if you disable the circuit but I've not seen this be the case myself.

I don't have Stargate, but Secret Quest does work on mine at least.  Forgot about that game, time to get it back out!

[nadir]

OK, mine is an A3.  I know it was purchased very late.  My cousin got it as a Xmas gift back IIRC in '92?  Doesn't mean that it wasn't sitting on a shelf for a long time though...  I guess one of these days I'll have to pop the case and check the chip dates to satisfy my curiosity.

[+Mitch]

The date code is actually the numbers/letters that are directly after the A1 or A3 or X. Usually in blue ink.

 

Mitch

[SearsRoebuck]

I can happily report that LadyBug works on my Atari 7800 - this is what freaked me out, another poster saying this exact game didn't work for them - as a copy I had bought was on its way to my place! Excellent port btw.  Dark Chambers 2600 seems like a poor trade off; though I'd be curious if Secret Quest and Stargate don't work on these systems for any one who has them. 

 

As to why I don't just play 2600 games on a 2600 - a combination of both space and the fact that the 7800 does play about 99.9% of the 2600 games. My system is an AT85, and has an early 'purple box' (matching serial) so it is before the systems were modified any. 

Edited July 8, 2020 by SearsRoebuck