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x=usr(1536)

Expansion Interface installation

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Since I don't seem to be able to find a solid answer to this question: if one were to have a 7800 without the Expansion Interface connector installed on the PCB, would it only be necessary to install the connector itself or are there other components that would be required in order for it to have a functional Expansion Interface?

 

This isn't something for which I have a specific use in mind; the question is being asked solely out of general curiosity.

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Both my 7800’s have the interface, but from pics of my boards, there doesn’t appear to be any discrete components directly adjacent or very near the lines that run to the connector. There are detailed 7800 schematics on AtariAge somewhere (do a Google search for “site:atariage.com 7800 schematics” and you’ll find them). You could check those to be sure, as well as follow the board traces to see if anything appears to be missing in the circuit paths. 

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37 minutes ago, DrVenkman said:

Both my 7800’s have the interface, but from pics of my boards, there doesn’t appear to be any discrete components directly adjacent or very near the lines that run to the connector.

Cool, and I appreciate the confirmation.

37 minutes ago, DrVenkman said:

There are detailed 7800 schematics on AtariAge somewhere (do a Google search for “site:atariage.com 7800 schematics” and you’ll find them). You could check those to be sure, as well as follow the board traces to see if anything appears to be missing in the circuit paths. 

Yup, already got 'em :-D  Just wanted to make sure that what the real world was seeing matched what they were saying.

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13 minutes ago, x=usr(1536) said:

Cool, and I appreciate the confirmation.

Yup, already got 'em :-D  Just wanted to make sure that what the real world was seeing matched what they were saying.

Sure thing. As it happens, my daily driver 7800 is currently open to look at. I’m having weird intermittent issues with the UAV I have installed in it and I can’t figure out if I’ve got a dodgy connection somewhere that I just can’t find, or if the UAV itself has a marginal solder joint on one of the SMD components. It’s running great “topless” so after running into the wall troubleshooting I just left it open for now. That’s a project for another day …

 

But in the meantime, that board is sitting there available for me to look at again after work and confirm. The only things installed super-close the connector are the pins for the RF modulator, which I have removed entirely from this machine. 

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4 hours ago, DrVenkman said:

The only things installed super-close the connector are the pins for the RF modulator, which I have removed entirely from this machine. 

She will never be the same. RF is life. 😁

 

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2 minutes ago, Jinks said:

She will never be the same. RF is life. 😁

 

Are you drunk? :) 

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1 hour ago, DrVenkman said:

Are you drunk? :) 

Pretty sure he must be... once you go UAV you really can't go back. The s-video from it has just spoiled me.

 

Course... I'm a bit biased since UAVs are kinda my thing ;)

 

 

BTW @x=usr(1536) There are no additional components. Just have to solder in a double set of right angle pin headers to the vias and you essentially have an expansion port. @CPUWIZ sometime back even posted a pic of doing that very thing on one of his and dropped some hints that we all might want to do the same in the future but didn't post more. It is one of the reasons I left the expansion port section alone with my UAV mount boards in the 7800.

 

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2 hours ago, -^CrossBow^- said:

BTW @x=usr(1536) There are no additional components. Just have to solder in a double set of right angle pin headers to the vias and you essentially have an expansion port.

Excellent, and thanks :)

2 hours ago, -^CrossBow^- said:

@CPUWIZ sometime back even posted a pic of doing that very thing on one of his and dropped some hints that we all might want to do the same in the future but didn't post more. It is one of the reasons I left the expansion port section alone with my UAV mount boards in the 7800.

Now that you mention it, I do vaguely recall him making threats of that variety :-D  FWIW, since I was planning on installing a UAV in the ugly 7800 (which has no expansion port), it seems like the ideal time to also install the expansion port.

 

Current plan is to keep the RF modulator after the UAV is in there - if I ever need to troubleshoot something related to the display, at least RF will be available.

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Posted (edited)
14 hours ago, John Stamos Mullet said:

RF is garbage

To each his own. I think some 7800 rf setups suck. Some are clear and the cool ghosting on galaga on an old crt to me is wild. No I am not drunk I just like things the way they were. As long as it is not snowy RF is ok. I have a 600xl with s video and composite and yeah it is clear the rf on it was shit so I can understand why to redo the video output section. 

Maybe your using a modern tv that can be another issue and a good reason for a  video mod. 

 

 

Edited by Jinks
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On PAL 7800's the RF is horrific, even on a CRT (at least mine was anyway). Maybe I just had a console with a duff RF but it was pretty gnarly.

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Both my NTSC 7800s, including a Warner-made AT84 serial number unit from early 1984, have terrible RF. Well, the AT84 has terrible RF - my other is now my daily driver, an A1 machine with a UAV in it. ;)  

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25 minutes ago, DrVenkman said:

Both my NTSC 7800s, including a Warner-made AT84 serial number unit from early 1984, have terrible RF. Well, the AT84 has terrible RF - my other is now my daily driver, an A1 machine with a UAV in it. ;)  

At various points from my original 7800 I get as a kid in 1987 and a variety of them I’ve picked up along the way through all of the varying serial numbers AT, A1, A3, X - RF was complete crap on all of them. The only console I’ve ever owned where the RF was decent was my original Coleco Gemini. Even all my Sega consoles have garbage RF.

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17 minutes ago, John Stamos Mullet said:

The only console I’ve ever owned where the RF was decent was my original Coleco Gemini.

My Sears Heavy Sixer has marvelous RF, and my Light Sixer is almost as good. My later-made 4-switch units have gross RF. One of my 5200's had okay RF but I've put a UAV into that one as well. 

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Weirdly enough, the 7800 I've had for 20-odd years has surprisingly good RF output.  You'd never confuse it for composite, but it's definitely better than it has any real right to be.

 

N.B.: this is not a deterrent to installing a UAV :-D

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9 hours ago, x=usr(1536) said:

N.B.: this is not a deterrent to installing a UAV :-D

It is also worth noting that putting in a UAV doesn't meant that the RF has to go either. I think I've only removed the RF modulator on maybe two 7800s sent to me over the past 5 years at the request of the console's owners. I've also installed UAVs in place of simple composite upgraded or 'HDMI' upgraded consoles that already had their RF modulator removed.

 

The point is that I don't remove the RF modulator when installing UAVs unless directed to do so. That is what I really like about the UAV since it doesn't require anything to be removed from the console for it to work and look good!

 

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On 6/20/2022 at 5:12 PM, -^CrossBow^- said:

Pretty sure he must be... once you go UAV you really can't go back. The s-video from it has just spoiled me.

 

Course... I'm a bit biased since UAVs are kinda my thing ;)

 

 

BTW @x=usr(1536) There are no additional components. Just have to solder in a double set of right angle pin headers to the vias and you essentially have an expansion port. @CPUWIZ sometime back even posted a pic of doing that very thing on one of his and dropped some hints that we all might want to do the same in the future but didn't post more. It is one of the reasons I left the expansion port section alone with my UAV mount boards in the 7800.

 

 

It would be useful to task the low-bandwidth Expansion Port with some task like sending scoring information - or "saving a game" - to a device like the SaveKey or an AtariVox instead of hogging the 2nd Joystick Port. Especially since we don't have a device that can act as a "hub" on Joystick Port 2 for multiple devices* like the unreleased 7800 keyboard could do [pass-thru for another controller, the keyboard functioning at the same time, and multiple SIO device support].

 

*Obviously ignoring the MultiJoy adapters here.

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3 minutes ago, Lynxpro said:

 Especially since we don't have a device that can act as a "hub" on Joystick Port 2 for multiple devices* like the unreleased 7800 keyboard could do [pass-thru for another controller, the keyboard functioning at the same time, and multiple SIO device support].

 

*Obviously ignoring the MultiJoy adapters here.

I was going to say... the QuadTari allows for this very thing provided a game is designed for its use. Also I would have to check the schematics again, but I seem to recall that the expansion port mainly just provides power and ground along with some video output and mainly video input signals. I don't believe it had anything in place in the way of the controller input lines on it.

 

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Posted (edited)
32 minutes ago, -^CrossBow^- said:

I was going to say... the QuadTari allows for this very thing provided a game is designed for its use. Also I would have to check the schematics again, but I seem to recall that the expansion port mainly just provides power and ground along with some video output and mainly video input signals. I don't believe it had anything in place in the way of the controller input lines on it.

 

 

From my understanding, the QuadTari doesn't support the 7800's 2nd Fire Button so it would seem like punting AtariVox type devices to the Expansion Port would be a better use since it would free up the 2nd Joystick Port so both players could retain Dual Fire Button support. The MultiJoy supposedly supports like a jillion* Single Fire Button Controllers but I'm not aware of any titles on the 2600 or 7800 that support them; they primarily seem to have their support on the Atari 8-bit side of things.

 

*Cal Worthington standard units. Go See Cal! And his dog Spot!

Edited by Lynxpro
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8 hours ago, Lynxpro said:

 

From my understanding, the QuadTari doesn't support the 7800's 2nd Fire Button so it would seem like punting AtariVox type devices to the Expansion Port would be a better use since it would free up the 2nd Joystick Port so both players could retain Dual Fire Button support. The MultiJoy supposedly supports like a jillion* Single Fire Button Controllers but I'm not aware of any titles on the 2600 or 7800 that support them; they primarily seem to have their support on the Atari 8-bit side of things.

 

*Cal Worthington standard units. Go See Cal! And his dog Spot!

Understood, but in looking at the schemes again for the expansion port..

 

image.png.121137d3b1d2f92980ea5bcca84f4929.png

 

Again, there isn't much here that can be used as the expansion port seems mostly designed for external video input purposes?

 

 

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37 minutes ago, -^CrossBow^- said:

Again, there isn't much here that can be used as the expansion port seems mostly designed for external video input purposes?

Yes, according to the 7800 schematic, the expansion port doesn't have any I/O capabilities: it only provides audio, video and sync from Maria and a few control signals so that the an external device can:
1 - disable the internal 7800 clock and provide an external one
2 - halt/resume the cpu and Maria chip

This allows to have the external and internal video generation to be synchronized, so that the two can be mixed together.

Any data transmission in both direction has to happen using the cartridge or controller ports, the expansion port alone is of no use for that.

 

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4 minutes ago, alex_79 said:

Yes, according to the 7800 schematic, the expansion port doesn't have any I/O capabilities: it only provides audio, video and sync from Maria and a few control signals so that the an external device can:
1 - disable the internal 7800 clock and provide an external one
2 - halt/resume the cpu and Maria chip

This allows to have the external and internal video generation to be synchronized, so that the two can be mixed together.

Any data transmission in both direction has to happen using the cartridge or controller ports, the expansion port alone is of no use for that.

 

Exactly, now I did mess with tapping signals from the expansion port for use with the UAV some months back, but found that not all the signals needed are actually present or their outputs were too different to work properly with the UAV directly. One of those missing signals is the color signal from the TIA as an example.

 

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Remember what this was intended for: to control an external LD player. That’s it. That’s the use case: some GCC guy wanted to do stuff like Dragon’s Lair on a 7800. To be fair, that would be kind of awesome. We could something similar today with solid state video and audio storage instead of a fragile mechanical LD player. 

 

Well, maybe someday once the semiconductor supply chain gets something closer to normal again. 

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On 6/28/2022 at 10:35 AM, DrVenkman said:

Remember what this was intended for: to control an external LD player. That’s it. That’s the use case: some GCC guy wanted to do stuff like Dragon’s Lair on a 7800. To be fair, that would be kind of awesome. We could something similar today with solid state video and audio storage instead of a fragile mechanical LD player. 

 

Well, maybe someday once the semiconductor supply chain gets something closer to normal again. 

 

I suspect the plan would've been to sell a specialized cartridge along with the LaserDisc disc itself. The cartridge serving the gaming logic specifically programmed for a certain LaserDisc title. So for Atari's own Firefox, they'd probably sell the bundle with the Firefox control cartridge and then the Firefox LaserDisc. 

 

Warner and certain Atari Inc execs would've liked that plan since Coleco had been rumored to have been exploring that too with a Colecovision Expansion Module. Although there had been chatter and rumors about both using either CED or LaserDisc. As having been part of a family with a CED player, that would've been a nightmare with all of the skipping caused by dust particles. Great picture quality compared to VHS but ugh, having to fast forward and rewind scenes just to get the dust particles away from the stylus so the video wouldn't skip.

 

Had things worked out differently and Atari Inc survived, I suspect they would've shelved those plans and retained the possibility of providing such gaming experiences with the 16-Bit Mickey console since it would've retailed for much more than the 7800 at Christmas 1985.

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On 6/28/2022 at 7:17 AM, alex_79 said:

Yes, according to the 7800 schematic, the expansion port doesn't have any I/O capabilities: it only provides audio, video and sync from Maria and a few control signals so that the an external device can:
1 - disable the internal 7800 clock and provide an external one
2 - halt/resume the cpu and Maria chip

This allows to have the external and internal video generation to be synchronized, so that the two can be mixed together.

Any data transmission in both direction has to happen using the cartridge or controller ports, the expansion port alone is of no use for that.

 

 How does synching not count as I/O if it's bidirectional by nature?

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