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The picture jumps in Asteroids


MaximRecoil
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The whole picture shifts slightly (maybe 1/16") up and down every few seconds in Asteroids. That isn't normal is it? It doesn't do it in the Stella emulator. I tried my Asteroids cartridge in a few different Atari 2600s (heavy sixer, light sixer, and a 4-switch woodgrain), as well as in my Atari 7800, and it does the same thing in all of them. None of my other cartridges do this.

Edited by MaximRecoil
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I just tried Asteroids on two different CRT TVs and the picture was perfectly stable on both of them. So apparently, my main TV (also a CRT) doesn't like Asteroids, which is bizarre, given that I don't have any issues on that TV with any other cartridge for Atari or any other game for any other console I own.

 

I wonder if there are any non-standard coding tricks used in Asteroids. Doesn't the Atari 2600 rely on the game code to generate an NTSC-compatible video signal? If so, it would be possible for some 2600 games to be more NTSC compatible than others.

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Possible bit-rot of the ROM, while rare it does happen. I think I've encountered it twice out of 500 or so cartridges.

 

Easy fix - Space Rocks :D

 

Hmm, the video's missing from the store front for some reason. Probably happened when the Box and Box-less versions were combined into one entry.

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Possible bit-rot of the ROM, while rare it does happen. I think I've encountered it twice out of 500 or so cartridges.

 

Easy fix - Space Rocks :D

 

Hmm, the video's missing from the store front for some reason. Probably happened when the Box and Box-less versions were combined into one entry.

 

You posted at about the same time that I made my second post, so you didn't see it. In any event, it isn't the cartridge, it's my TV.

 

I'm aware of Space Rocks, and it would be a nice game to have, but I'm also nostalgic about the original Asteroids cartridge. It was 1 of the 5 games I bought the same day I bought my first Atari when I was 10 years old in 1985.

Edited by MaximRecoil
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I wonder if there are any non-standard coding tricks used in Asteroids. Doesn't the Atari 2600 rely on the game code to generate an NTSC-compatible video signal? If so, it would be possible for some 2600 games to be more NTSC compatible than others.

 

It's possible, Warlords generated the sync signal incorrectly and confused the XRGB-mini when used with that new RGB mod. I fixed that ROM, it's available in my blog.

 

I took a quick look at Asteroids and it's doing the same thing, setting VSYNC before WSYNC instead of after:

post-3056-0-09917500-1444746025_thumb.png

 

Do you have a Harmony cartridge? If not, I highly recommend getting one.

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It's possible, Warlords generated the sync signal incorrectly and confused the XRGB-mini when used with that new RGB mod. I fixed that ROM, it's available in my blog.

 

I took a quick look at Asteroids and it's doing the same thing, setting VSYNC before WSYNC instead of after:

attachicon.gifScreen Shot 2015-10-13 at 9.19.16 AM.png

 

Do you have a Harmony cartridge? If not, I highly recommend getting one.

 

Thanks for looking into that.

 

No, I don't have a Harmony cartridge. And that sucks about Warlords; I just bought that game (it hasn't arrived yet), and it will probably do the same thing on my main TV that Asteroids is doing. I wish Atari 2600 cartridges could be opened up without ruining the label; then I could possibly have a new, fixed ROM burned for games like this. I suppose a Harmony cartridge would make more sense, but I like dedicated cartridges and their labels, that simply boot to the game you want to play immediately.

 

Would it be hard to fix the Asteroids ROM? I'd like to have a fixed version in case I get a Harmony cartridge.

Edited by MaximRecoil
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No, I don't have a Harmony cartridge. And that sucks about Warlords; I just bought that game (it hasn't arrived yet), and it will probably do the same thing on my main TV that Asteroids is doing. I wish Atari 2600 cartridges could be opened up without ruining the label; then I could possibly have a new, fixed ROM burned for games like this. I suppose a Harmony cartridge would make more sense, but I like dedicated cartridges and their labels, that simply boot to the game you want to play immediately.

 

Would it be hard to fix the Asteroids ROM? I'd like to have a fixed version in case I get a Harmony cartridge.

 

If it does check out Medieval Mayhem, my take on Warlords. Hmm, that video's missing too...

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I've noticed that progressive scan CRT televisions don't do too great with some of my games. Check to see if you have the Red, Blue and Green component connections for more modern systems on your TV. I have two sets that have this and neither does well with my Atari games. My HD's do fine, as do my non-component TV's.

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I've noticed that progressive scan CRT televisions don't do too great with some of my games. Check to see if you have the Red, Blue and Green component connections for more modern systems on your TV. I have two sets that have this and neither does well with my Atari games. My HD's do fine, as do my non-component TV's.

 

My TV has component (YPbPr) inputs, but it isn't capable of progressive scan (at least not of the ~480p variety, which is ~31 kHz). It handles progressive scan of the ~240p variety just fine (~15 kHz), as do nearly all CRT TVs ever made. Most, if not all, consoles prior to the Sega Dreamcast output a ~240p signal, which is why you can see "scanlines" on them. The Dreamcast defaulted to 480i, which is also ~15 kHz.

 

In any event, I bought this TV new 10 years ago, and I've connected practically every major console made between the Atari 2600 and the PS2 to it, and I've never had an issue with any game before. Granted, I haven't played a lot of different Atari 2600 games on it; I usually stick with a handful of favorites when I'm in the mood to play Atari.

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And that sucks about Warlords; I just bought that game (it hasn't arrived yet), and it will probably do the same thing on my main TV that Asteroids is doing.

 

Warlords came in the mail today, and its picture is perfectly stable on my main TV, so I don't know what's going on with Asteroids. Weren't there two versions of Asteroids, one with the "©1981, Atari Inc." splash screen and one without? Mine has the splash screen. I wonder if the version without the splash screen would be any different. Oddly enough, the picture is perfectly stable on that splash screen; it doesn't start jumping until it goes into "attract mode", and continues to jump when you are playing the game.

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Warlords came in the mail today, and its picture is perfectly stable on my main TV, so I don't know what's going on with Asteroids.

Darrell has already told the problem. Asteroids is not syncing to the TV correctly. This a real easy fix. There is a LDX #$FF instruction that can be changed to TSX, and then the VSYNC routine from Macro.h can be used. The values for TIM64T also have to be updated, but that's about it.

 

 

I don't have time to fix it right now, so maybe someone else will. You would also need a Harmony cart.

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Darrell has already told the problem. Asteroids is not syncing to the TV correctly.

 

Yes, and he said Warlords has the same problem, yet Warlords is perfectly stable on the same TV, so that changes things. And this doesn't look like any sync issue I've ever seen; the picture isn't rolling; it is shifting ever so slightly (about 1/16") up and then immediately back down, and it repeats that every couple/few seconds. Also, why is the splash screen perfectly stable? Here's a video:

 

Edited by MaximRecoil
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Yes, and he said Warlords has the same problem

It does have the same problem, VSYNC is hit before WSYNC instead of after.

 

When VSYNC is hit after WSYNC it ends up being triggered at cycle 3 (can also consider it as cycle 79 as a scanline takes 76 cycles).

 

For Asteroids it's being triggered at cycle 22.

 

For Warlords it's triggered at 62.

 

Also, why is the splash screen perfectly stable?

The splash screen in Asteroids is hitting it at cycle 55. Once the splash screen goes away it hits it at 22. For your TV hitting it between 55 and 79 is probably OK, while 22 is not.

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  • 7 years later...

I love keeping old topics alive :)

 

So I have worked on a few and this same issue has finally cropped up for me. Where the console is going to be re-homed I do need to resolve the issue, not create a workaround. I did notice it isn't just every few seconds that it jumps slightly as would be easy to assume, it is whenever an asteroid is entering the play field from the top of the screen. So it is a sprite causing the instability. I've tried the obvious and swapped in a set of known working IC chips and will swap a few other components that are known working to hopefully isolate the issue. If the additional information of when it happens helps and anyone has any clue what a possible fix could be, I'd love to see this thread expanded. Note: I did take this console and try the same game on a 13 inch CRT that is hooked up to my "Retro" setup and the picture IS stable. So odd, LOL!

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I've had this happen with a few games on the TV I use 99% of the time.  As soon as I switched to another TV ,  the picture stopped jumping. 

 

I guess I should also mention that it is mainly homebrews ( 2 or 3) that this happened with.   

 

Another problem I had with my main TV is the picture is too high and gets cut off at the top of the screen.   And once again trying another TV fixed the problem.

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13 hours ago, JeffsFort said:

I've tried the obvious and swapped in a set of known working IC chips and will swap a few other components that are known working to hopefully isolate the issue.

You can't fix that by changing components, as it is not an hardware problem, but a software one. The code in those games produces an out of specs TV signal that some TVs do not like. The only solution is to have a new cartridge made with a fixed rom (or play the fixed rom in a flashcart).

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8 hours ago, alex_79 said:

You can't fix that by changing components, as it is not an hardware problem, but a software one. The code in those games produces an out of specs TV signal that some TVs do not like. The only solution is to have a new cartridge made with a fixed rom (or play the fixed rom in a flashcart).

That makes SpiceWare's response make much more sense. Thanks alex_79!

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