Atari 2600 RGB mod

[Grimakis]

I am pretty sure there are more ROMs which will face the same problem. Instead of hacking them all, wouldn't it be a better idea (if possible) to make the XRGB-mini a bit more tolerant (like CRTs are)?

 

I had a brief look at the Warlords code. It seems that it produces the VSYNC signal for ~3.2 scan lines (starting with the 0.2 or ~14 cycle scan line). AFAIK at least 3 scan lines are required. I don't know about a requirement that partial scan lines are forbidden. So Warlord seems to met the specs.

The newer Framemeister firmwarw has a Sync-Time option. If you put it on 10 or 100 instead of 3, it ublocks the Framerate, but games that drop sync still work.

 

Try Joust(after you die and it cycles the tittle sceen) and try The Empire Strike Back(after you destroy and AT-AT)

[+SpiceWare]

Oh nice. That appears to fix it. Thanks. I guess the XRGB-mini isn't quite as tolerant to incorrect timing as a CRT. If you manage to fix the king position I for one would be happy.

I'll see what I can do this weekend. Until then, play Medieval Mayhem.

[collinp]

I am pretty sure there are more ROMs which will face the same problem. Instead of hacking them all, wouldn't it be a better idea (if possible) to make the XRGB-mini a bit more tolerant (like CRTs are)?

 

I absolutely agree. That is assuming we can find an XRGB setting that fixes the issues. I like Warlords quite a bit so I'm grateful for a hack in the meantime. Plus the hack gives some insight into what the XRGB doesn't like.

 

The newer Framemeister firmwarw has a Sync-Time option. If you put it on 10 or 100 instead of 3, it ublocks the Framerate, but games that drop sync still work.

 

Maybe this is the setting we're looking for. I'll try it this weekend.

 

I'll see what I can do this weekend. Until then, play Medieval Mayhem.

 

If it's easy. It's possible we'll find a setting to make the original game work and I wouldn't want you to waste your time.

 

Medieval Mayhem is a pretty impressive piece of work. Hard to believe we're still able to push the Atari even further than they did in the 80s.

Edited August 21, 2015 by collinp

[+SpiceWare]

If it's easy. It's possible we'll find a setting to make the original game work and I wouldn't want you to waste your time.

I probably won't get to it until Sunday, so post something if you figure out a solution before then.

 

Medieval Mayhem is a pretty impressive piece of work. Hard to believe we're still able to push the Atari even further than they did in the 80s.

Thanks! The difference between Warlords and Medieval Mayhem is ROM is now super cheap. Warlords had to be squeezed into 4K while Medieval Mayhem used 32K. 6K alone was used for Medieval Mayhem's menu, that's why the games back then used a printed Game Matrix in the manuals.

 

Have you checked out Draconian? That's using modern technology (specifically an ARM chip in the cartridge) to push the Atari beyond what was possible back in the day. The most recent ROM is actually in my blog, not in that homebrew topic.

[collinp]

I am pretty sure there are more ROMs which will face the same problem. Instead of hacking them all, wouldn't it be a better idea (if possible) to make the XRGB-mini a bit more tolerant (like CRTs are)?

 

 

The newer Framemeister firmwarw has a Sync-Time option. If you put it on 10 or 100 instead of 3, it ublocks the Framerate, but games that drop sync still work.

 

Try Joust(after you die and it cycles the tittle sceen) and try The Empire Strike Back(after you destroy and AT-AT)

 

 

I probably won't get to it until Sunday, so post something if you figure out a solution before then.

 

I tried Joust and have seen no issues when cycling back to the title screen. I tried Empire Strikes Back and had no issue after destroying an AT-AT

 

I tried various XRGB-mini settings with Warlords. The best combo I can find is to set Sync Time to 100 and Sync Mode to Off. I believe Sync Time 100 is setting a long time before the XRGB decides it's lost input lock and Sync Mode Off is decoupling the input and output frame rate. With this combo the Warlords image stays on the screen, but hops up or down a scanline every few seconds. It's certainly playable but not perfect.

 

It's pretty clear at this point that this is not a 2600RGB issue. If anything this proves how faithful the 2600RGB is to the original video timings. This appears to be a game with unusual timing characteristics that the XRGB-mini doesn't tolerate well over RGB. I am curious if other games like this will be found.

[Thomas Jentzsch]

I tried various XRGB-mini settings with Warlords. The best combo I can find is to set Sync Time to 100 and Sync Mode to Off. I believe Sync Time 100 is setting a long time before the XRGB decides it's lost input lock and Sync Mode Off is decoupling the input and output frame rate. With this combo the Warlords image stays on the screen, but hops up or down a scanline every few seconds. It's certainly playable but not perfect.

 

It's pretty clear at this point that this is not a 2600RGB issue. If anything this proves how faithful the 2600RGB is to the original video timings. This appears to be a game with unusual timing characteristics that the XRGB-mini doesn't tolerate well over RGB. I am curious if other games like this will be found.

I tend to disagree.

 

It may well be, that some timing in Warlords is unusual, but AFAIK no one has even reported similar problems with Warlords before. So either XRG-mini is more sensitive to wrong timings than the original hardware or it makes an always existing sync problem much more obvious. I know it seems unfair, that you have to reproduce old software flaws correctly, but IMO that's what it takes to be 100% compatible.

 

BTW: I did a very simple search in my ROMs and found Gangster Alley (here VSYNC is enabled for ~2.7 scan lines). Someone should test it.

 

More findings: Missile Command, Dodge'em, Holey Moley, Tempest (prototype)

 

Also the PAL versions of Pick'N'Pile and Acid Drop show similar code. But when converting to NTSC, someone has changed that code. Maybe there was a good reason for it?

Edited August 22, 2015 by Thomas Jentzsch

[collinp]

I tend to disagree.

 

It may well be, that some timing in Warlords is unusual, but AFAIK no one has even reported similar problems with Warlords before. So either XRG-mini is more sensitive to wrong timings than the original hardware or it makes an always existing sync problem much more obvious. I know it seems unfair, that you have to reproduce old software flaws correctly, but IMO that's what it takes to be 100% compatible.

 

BTW: I did a very simple search in my ROMs and found Gangster Alley (here VSYNC is enabled for ~2.7 scan lines). Someone should test it.

 

More findings: Missile Command, Dodge'em, Holey Moley, Tempest (prototype)

 

Also the PAL versions of Pick'N'Pile and Acid Drop show similar code. But when converting to NTSC, someone has changed that code. Maybe there was a good reason for it?

 

I'm thinking this is an XRGB-mini issue because it does not happen on a BVM with an RGB signal and it does not happen with the 2600RGB's s-video or composite through the XRGB-mini. But who know you may be right it could be a 2600RGB bug.

 

I see no problems with Gangster Alley, Missile Command, Dodge 'em, Holey Moley, or Tempest (prototype).

 

I did find another ROM that's not too happy with RGB. Aquaventure (prototype). Over RGB to the XRGB it displays an image but has a lot of vertical shaking. It also has no problems over s-video on the XRGB-mini.

[Thomas Jentzsch]

Thanks for testing. Looks like the problematic code is not as obvious as I thought. Maybe comparing with Aquaventure will help.

 

In Warlords and Aquaventure the timing for enabling VSYNC varies slightly. In Gangster Alley And Missile Command VSYNC seems to be always enabled at the same cycle. Therefore in the problematic games, the length of the VSYNC signal varies a bit. Maybe that's a problem for XRGB-mini?

[darcagn]

I would say this issue is with the XRGB-mini. It's not unusual for a specific game to give it issues. There are certain games on SNES, for example, that drop sync or cause the screen to bob up and down when a certain type of event happens.

[+SpiceWare]

Try Canyon Bomber, it holds VSYNC for something like 14 scanlines.

 

My 1084S can handle PAL games just fine, but it doesn't like Canyon Bomber at all.

[+SpiceWare]

Oh nice. That appears to fix it. Thanks. I guess the XRGB-mini isn't quite as tolerant to incorrect timing as a CRT. If you manage to fix the king position I for one would be happy.

 

Ended up fixing it this morning. You can find it in my blog.

[collinp]

Yes, if it were a simple on/off switch between the two original pal and ntsc palettes I would have put it in place of the useless channel switch. But as it's automatic and I don't have pal60 games anyway, I won't install any switch. People with a lot of Pal60 games would probably have preferred the option of a manual two position switch, as it would give a tactile feedback of what palette you are using. A push button may be confusing sometimes.

 

jarreboum's post got me thinking that it would be nice to use the channel switch for a palette switch. I don't intend to use RF again and the switch will be just sitting there unused on a 4 switcher. After some searching I found a momentary switch that is a near perfect replacement for the normal dual throw channel switch.

 

C&K Components L112022ML04Q

 

Available from Mouser here :

 

http://www.mouser.com/ProductDetail/CK-Components/L112022ML04Q/?qs=%2fha2pyFaduiTtMo24X4GBTvNpiYC5gPBTBmqwgkiexxVfRTku62AKw%3d%3d

 

Here is photo comparing the momentary switch on the left with a standard Atari dual throw switch on the right.

 

 

Below is some information on how I installed the switch in my system.

 

*** I am not responsible if you kill your console with this information. ***

 

When the switch is installed on the board the default position is to the right (Channel 3). This connects +5V to the center pole. Pushing the switch to the left connects the center pole to ground and then it springs back to the right position. The ground connection is fortunately exactly what we want for palette selection, but we need to do something about the 5V.

 

Cutting off the pin on the switch which connects to 5V is not a solution. I sacrificed a switch so you don't have to. With just two pins holding the switch on the board it can twist fairly easily when you push it. With all 3 pins soldered down the switch has a very solid feel.

 

I thought about putting a diode on the center pole so 5V can't flow into the 2600RGB palette switch, but I felt more secure cutting the 5V connection to the switch entirely. The copper is quite wide and thick for this trace. Unlike cutting traces on later systems an X-acto Knife wasn't cutting it, so I used a small Dremel sanding bit to disconnect the trace.

 

 

The center pole connects to the RF circuit for channel selection. I removed the connection to the RF circuit and used the through-hole on the board to mount an angled pin connector which is connected to the "P" pin on the 2600RGB.

 

 

Though I don't intend to use it I decide to fix the RF circuit that I just broke. You can either tie the pin removed to ground on the RF can for channel 2 or tie it to the resistor that the 5V rail terminates at for channel 3. I chose channel 3 since that is the default switch position. Note the wire from the vertical RF board to the pink resistor in the photo below.

 

 

Final install photos. It looks factory to me.

 

I'll remove the unnecessary jumper wires eventually. I'm still experimenting with the AV connections.

 

 

[collinp]

 

Ended up fixing it this morning. You can find it in my blog.

 

Works like a champ. Thanks.

[glazball]

Great work collinp! That channel select is the perfect spot for a palette switch! From the pics darcagn posted, it would seem that some palettes are better for some games than others. Still hoping to hear more info on that because my preference would be to leave out the palette switch entirely if possible. However, I have no problem with it in the channel select spot, looks natural!

 

Mind posting a pic of the rear of your system? I'm eager to know if installation, including audio, can be done with a single 8-pin mini DIN. If so, is it just a question of having better shielded cables?

[spawnshop]

That is sweet @collinp

[collinp]

Great work collinp! That channel select is the perfect spot for a palette switch! From the pics darcagn posted, it would seem that some palettes are better for some games than others. Still hoping to hear more info on that because my preference would be to leave out the palette switch entirely if possible. However, I have no problem with it in the channel select spot, looks natural!

 

Mind posting a pic of the rear of your system? I'm eager to know if installation, including audio, can be done with a single 8-pin mini DIN. If so, is it just a question of having better shielded cables?

 

There are 3 palettes. #1 I would call natural, #2 I would call vibrant, #3 I would call garish. I prefer #1 and honestly don't see myself having a big desire to change it. I can definitely imagine that some people will like #2 because the colors pop more. I'm kind of confused as to what #3 is for as I've yet to see anything that looks right with it.

 

The palette switch can also be used to pause the Atari. Like all Atari pause mods the console does not generate a valid video signal when paused. I'm using an XRGB-mini and it takes a couple seconds to resync the video on unpause. Since most Atari games are action oriented those several seconds can be critical. As such I don't see myself using the pause mode very often either. Those with CRT TVs may find it much more useful.

 

I've got a Sixer with an s-video mod that I plan to swap out for a 2600RGB. That console doesn't have a channel switch and I'm loath to drill holes for a switch. I will likely not externalize the palette switch on that install. I think it will be fine. I did not externalize the palette switch on my NES either and I'm happy with that decision.

 

The back of this Vader may be a little underwhelming. I just swapped the mini-DIN 8 for the RF cable.

 

 

I just added some leads for audio since there are no pins for audio on Tim's mini-DIN 8 board.

 

 

Audio seems good enough for me over the mini-DIN 8. If I crank the AV system I can definitely hear some noise, but I can hear noise even with the separate audio jack that Tim includes with the kit. The Atari wasn't exactly designed for audiophiles. There may be slightly more noise in the mini-DIN 8 cable than the separate audio jack but they're pretty close. At normal listening levels the noise floor seems fine. I have a longer mini-DIN 8 cable that I was thinking would be a good replacement for the RF cable as it is a similar ~12 foot length. That cable definitely exhibits noticeably more noise. The noise is clear at lower volume levels than the shorter cable, but those volume levels are still higher than I'd want to play Atari on so it might still be an option.

 

Since I've found a few ROMs who's video timings don't play nicely with the XRGB-mini's RGB input I have been exploring installing a Nintendo multi-AV connector so I have the option to choose s-video, composite, or RGB all from the same port. Currently I have the mult-AV wired up but not mounted. I'm just using the Atari with the top off and accessing the connector that way. It's a convenient way to compare game behavior on RGB vs. S-video. I haven't decided what I'm going to do with this Vader. It might get the Nintendo connector. I really don't want to drill holes in the Sixer so I'm almost certainly going with a mini-DIN 8 tethered cable there.

 

Edited August 24, 2015 by collinp

[collinp]

I calibrated the s-video / composite input on the XRGB-mini the best I could. Strangely it doesn't appear to have a contrast control, but I got it pretty close to correct with patterns from a DVD player.

 

Here are some comparison shots with the XRGB calibrated.

 

These are all with Palette setting #1 which looks a lot like the Stella emulator "Standard" palette.

 

2600RGB - Composite

 

 

2600RGB - S-Video

 

 

2600RGB - RGB

 

 

[funkwad]

Hey all - pretty cool mod here...

 

Novice question - anyone know if you can install the Pause switch mod with the RGB mod? Interested in possibly doing both, and mayyybe the RF switch mod instead of controller mod.

 

Thx

[collinp]

Hey all - pretty cool mod here...

 

Novice question - anyone know if you can install the Pause switch mod with the RGB mod? Interested in possibly doing both, and mayyybe the RF switch mod instead of controller mod.

 

Thx

 

The 2600RGB mod has a pause mod built right in. No additional mod necessary. It's disabled by default but if you hold the palette switch down for 30 seconds you can enable it. Then a brief tap on the palette button pauses or un-pauses the 2600. The 2600RGB remembers if the pause feature enabled even if power is lost.

 

 

The palette switch performs different functions depending on how long you hold the button down.

• < 0.4s = Pause toggle. A quick tap of the button will pause/unpause the console. Because this is a hardware pause of the CPU, the video signal will cut out while the console is paused.
• < 2.5s = Select next palette.
• < 10s = Select palette #1.
• < 20s = Automatic PAL/NTSC game detect toggle. Enabled by default. This will allow only the selection of PAL palettes for PAL games and NTSC palettes for NTSC games. It uses the refresh rate to determine the game type. This should be disabled to play PAL60 homebrew games with correct colours.
• < 30s = Pause toggle. Disabled by default. The pause feature may be annoying for some people so it is disabled by default.

 

Note that all pause mods cause the video signal to drop since the game is what is generating the video timing and it's been paused. The video signal will resume after the game us un-paused. If you are using a CRT the signal should recover quickly, but if you are using something like the XRGB-mini the signal may take a second or two to re-sink and by that time you may be dead!

[netspecter]

Any news when the 2600RGB will be available from the US distributor? I held off ordering directly from Tim because I figured as soon as I did it would be available locally. That was a few weeks ago... I think I chose poorly.

[collinp]

I think things got a bit delayed because of the "startup bug". I just got my 2600RGB board with the fix in the mail today. So fixed boards are hitting US shores. Perhaps that's good news for the US distributor? Who knows.

 

As pleasant surprise I also received my 2600RGB kit for the Sixer.

 

Tim, is the Sixer installation guide going to be posted soon?

 

I can probably figure it out, but the 4 switch had some subtlties like laying down some components that might have left me guessing without a guide.

[darcagn]

Still haven't gotten my updated board yet I figured it would be here by now. Probably will be soon, though.

[ApolloBoy]

Just got my updated board today and finished up my installation. I ran into a minor issue unrelated to the 2600RGB installation but it's working great now and it looks even better than S-video!

[darcagn]

Got mine in today, swapped over the sockets and headers, finished installation, works great.

 

Finally can get that Atari off of my bench.

[Colmino]

I calibrated the s-video / composite input on the XRGB-mini the best I could. Strangely it doesn't appear to have a contrast control, but I got it pretty close to correct with patterns from a DVD player.

 

Here are some comparison shots with the XRGB calibrated.

 

These are all with Palette setting #1 which looks a lot like the Stella emulator "Standard" palette.

 

2600RGB - Composite

 

pitfall_2600rgb_composite.png

 

2600RGB - S-Video

 

pitfall_2600rgb_svideo.png

 

2600RGB - RGB

 

pitfall_2600rgb_rgb.png

 

 

So this seems to be the most concrete evidence that the RGB is a bit too dim. If I had one of these installed, I'd probably opt for the svideo out, which is reasonably adequate and doesn't seem to have the dimness issue.