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Member Since 7 Sep 2006
OFFLINE Last Active Feb 13 2019 2:08 PM

#4113509 CD4050 A/V mod on PAL atari 2600

Posted by alex_79 on Fri Sep 14, 2018 2:49 PM

The original jack briefly shorts the power supply to ground each time you insert or remove the plug, so that's another good reason to replace it.


Another mod I added which you can't see is a front 9 pin joystick connector hidden under the the lip of the console, a bit like how the 5200 and 7800 had theirs, but this port is connected to just the direction, action buttons and ground of the left controller. The other 3 pins I intend to connect to the action button, up and down of the second joystick port, so when I make my arcade stick, I can plug it in to this front port and have 4 action buttons for Stargate (Defender II), and the frontal port still be compatible with the standard Atari joystick at the same time, and still have the back ports for things like paddles.

Very clever! Stargate is one of the games I had as a kid, but actually I never used the second joystick: I only had two proline joysticks at the time and you can't easily press the button or move the stick on those unless you keep them in your hand...

#4113367 CD4050 A/V mod on PAL atari 2600

Posted by alex_79 on Fri Sep 14, 2018 11:21 AM

I appreciate the appreciation, thanks!icon_smile.gif

And thanks for posting pics of your mod. That's really well put together, I wish I could do such a nice and clean job! (there's a reason why I didn't posted pictures of my finished mod...icon_mrgreen.gif )
I like the use of the mini-din connector for all the audio and video signals (especially on the jr, where space is very limited). And, it seems that you also replaced the 3.5mm audio jack with a barrel connector for power. That's a good idea!


#4113097 Seal to Whales from Datatech Enterprises discovered

Posted by alex_79 on Fri Sep 14, 2018 3:05 AM

Great find!
I hope the rom can be dumped for preservation.

I just had a look at the entry for this game on Atarimania, and it lists it as a different version of "Frisco".
Probably that seemed reasonable by looking at the game description on the box, but after seeing the screenshots, it's clearly a different game.

#4113053 Coleco Gemini Controllers

Posted by alex_79 on Fri Sep 14, 2018 12:37 AM

Do you need the Y cable to play 1 player paddle games, or can you plug the controller directly into port 1?

If you don't mind to move the stick to the right instead of using the controller button, you can plug directly the controller and play most single player paddle games. There are a few exceptions, though: some games assign the paddles to the two player in inverted order. This is not a problem with a standard paddle set as you have both of them, so you just try to see which one you need to use, but of course such games are not playable with a gemini controller plugged directly into the port, because the other paddle just isn't there.

They're playable with the Y-adapter, even if you only have a single gemini controller: if it doesn't respond, it just means you have to plug it into the other port of the Y-adapter.

The following games won't work with a gemini controller without the Y-cable:

Demons to Diamonds
Street Racer
Video Olympics
Canyon Bomber
Star Wars - Jedi Arena

Im guessing that if you want to use the Gemini paddle on a regular 2600, youll need the Y cable?

There's no difference in using the controller with a gemini console or a regular Atari. In either case the Y-adapter allows to play 2 player games (or single games with swapped paddle order) and makes the button functional.

#4112349 Stella in Ubuntu 18.04

Posted by alex_79 on Thu Sep 13, 2018 8:57 AM

Try starting it from a terminal, to see if you get some error message that can help identify the problem.

#4112219 Coleco Gemini Controllers

Posted by alex_79 on Thu Sep 13, 2018 3:23 AM

The only strange thing from your descritpion is that you should have to move the stick right, not up to shoot the ball. That's because those controllers are not supposed to be plugged directly to the console when used as paddles, but instead the gemini console included an Y-cable that

1 - allowed to plug two controllers per port (like standard atari paddles that are paired)

2 - redirected the buttons to the right pins needed for paddles, so you can use them instead of moving the stick.

If you can solder, I made a schematic for the adapter that you can find here:

  • jhd likes this

#4112215 Beta test for the next major release of Stella

Posted by alex_79 on Thu Sep 13, 2018 3:19 AM

Well, I manged to test the new sound core a bit and I'm happy to report that I haven't anything to report....icon_biggrin.gif

I recorded samples of real hardware (unmodified, using rf connection) and from Stella 5 and 6 and played them back to back to easily spot any difference. The new audio core sounds like my real hardware in all the games and demos that I tested, while the difference with Stella 5 is evident in many cases.

On my old PC Stella 6 only reports a few audio buffer underruns when selecting the "Ultra quality, minimal lag" preset in the Audio dialog and only on certain roms (e.g. Draconian, Pitfall II and some demos). I can eliminate those by setting "Headroom" to 1 frame, and keeping 96000Hz samplerate and Ultra resampling quality, but when using custom settings I cannot choose Fragment size less than 512 bytes, and the preset uses 128 bytes (I opened an issue on github for this).

BTW, I think it could be useful a down to earth explanation of the meaning of each setting for the uninitiated like me and how they affect performance vs quality.


Thanks for your amazing work!icon_thumbsup.gif


#4111534 NTSC-PAL Conversions

Posted by alex_79 on Wed Sep 12, 2018 6:02 AM

There's also this thread: https://atariage.com...59-pal60-roms/


And check the "Supercharger conversions hacks" by Nukey Shay: many of those hacks are available in both TV format or with "palette select" function (use the COLOR/BW swutch to select between NTSC/PAL60).


#4110782 Arkyology - New prototype discovered - Finished Game!

Posted by alex_79 on Tue Sep 11, 2018 3:17 AM

[...] But my opinion is still the same. [...]

You mean, your opinion about emulators gathered from NOT having or using emulators?



Please, keep expressing your thoughts, I always like to read carefully reasoned arguments.


#4105387 AtGames 2018 speculation thread

Posted by alex_79 on Tue Sep 4, 2018 8:20 AM

I noticed there is a "5" before Stella in the manual.  Does this mean they are using version 5 or maybe it could be for something else, like a footnote?

The fact that there's a "REWIND" button on the joystick pretty much confirms that the device is using Stella 5: rewind during gameplay is a feature that was only  added in version 5.1.

#4103962 Arkyology - New prototype discovered - Finished Game!

Posted by alex_79 on Sun Sep 2, 2018 2:32 AM


What's an F8 cartridge?

F8 is one of the bankswitching methods used in 8k carts.
http://blog.kevtris....600 Mappers.txt

#4102664 RetroN 77

Posted by alex_79 on Fri Aug 31, 2018 4:12 AM

The super-crisp HDMI display is the main reason I finally caved. I also own a Flashback 2, and was tired of its blurry composite-only output.

I actually can't stand an unfiltered image with perfectly square pixels, it really ruins the 8-bit graphics IMO, especially if displayed on a big 50+ inch TV. Without some smoothing the individual pixels become too evident making the displayed objects less recognizeable, and the whole image look "flat" to me. That's another reason for me to not even consider getting a r77 unless the upcoming Stella 6 is ported to it.

Stella has highly configurable crt filters, scanlines and, since version 5, a new phosphor mode that better simulates phosphor persistence of a crt display. Personally, that's the only way I enjoy playing the atari 2600 on a modern TV set. An original console never looks that good on a digital TV, no matter what expensive mod and/or upscaler you get.

On a dedicated device like the r77, you have to sacrifice most of the configurability of the PC version of the emulator to keep it easy to use, but a couple of presets with different level of crt emulation in addition to the raw unfiltered image should do the job.

Here are some screenshots with example of filtered displays compared to "raw" ones (both taken in Stella 6 beta) to show what I'm talking about. (You can see the phosphor persistence effect in fast moving objects in "Galaxian" and "Super Break Out". It's really a dynamic effect that needs to be seen in action rather than on a screenshot, but it gives an idea). Note that the smoothing doesn't cause any loss in resolution: every single pixel of the Atari display is visible in the filtered images.
frogger_crt.png frogger_raw.png

galaxian_crt.png galaxian_raw.png

superbreakout_crt.png superbreakout_raw.png

#4099277 Games that should be redone

Posted by alex_79 on Sun Aug 26, 2018 3:00 AM

Do you think Star Wars Arcade could be improved with enhanced controls and maybe better graphics?

There's the Trak-Ball version:


#4099276 VCS/2600 Game Rarity by Number of Known Copies

Posted by alex_79 on Sun Aug 26, 2018 2:57 AM

The 1 verified copy has not been dumped or at least has not been publicly shared if the owner did dump it.

Not long ago though a member here found the code though and entered it in to make a Rom. But he has not shared that and planned to do a repro run but apparently has never got to it sadly because of health reasons.

But that shell has everything wrong about it and why would it be in Australia to begin with?

I like how the seller says they know very little about this game...Yeah other than it's a shitty fake they made! Lol


Not only the shell, but also the artwork and the font used in that label don't match the known cart.

This render of the label I posted years ago is much closer to the real thing.


350 USD? I'd say 50 cents would be a more fair price...


#4085534 VDEL

Posted by alex_79 on Sat Aug 4, 2018 11:57 PM

You need to write to P0, P1 and then P0 again if you want to change the ouptut of both players while VDEL is enabled.

The mechanism isn't very complicated once you understand the basics:

There are 2 registers for each player in the TIA: "new" (the one at the top in the stella debugger) and "old" (at the bottom).
When you write to GRPx in your code, 2 things happen:
1 - the value you're writing is stored in the "new" register
2 - the content of the "new" register of the other player is copied in the "old" register

The key part is that this mechanism is always in place, no matter if VDEL is enabled or not.

What VDEL does is just select which one of the two registers is used for the actual output to the screen. If VDEL is enabled, the "old" register is used, if it's disabled, the "new" one will be shown instead.

So, suppose that the value of  both GRP0_new and GRP1_new is $F0. If VDEL is enabled, the actual output for the two players is whatever is stored in their "old" registers.
If you want the output to be $01 for both, you proceed like this:



- store $01 to GRP0
GRP0_new is now $01, GRP0_old stays the same it was before, while GRP1_new ($F0) is copied to GRP1_old.

- store $01 to GRP1
GRP1_new is now $01, GRP1_old stays as it was ($F0), GRP0_new ($01) is copied to GRP0_old.

- store "anything" to GRP0
GRP0_new takes the new value, GRPO_old stays $01, GRP1_new ($01) is copied to GRP1_old.


Now the ouptut is $01 for both players.