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Double TIA chip idea!


SoundGammon
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Years ago, I tried stacking a 6532 chip on top of the one in my 2600 thinking I could double the ram! It worked, but no change! DUH! I know!

 

Anyway, I don't have quick access to all my 2600s and I thought about stacking another TIA chip on the other in a 2600 and see what would happen!

 

Less flicker in Pac-Man or Asteroids? Better video-color?

 

Anyone want to try this?

 

If you're carefull, you shouldn't have to solder it on, just push it, TIA, on top on the one in the 2600 and power it up!

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It'd be interesting to see a custom VCS mod where you have a split scree, one TIA handling the top, the other the bottom.

 

This is a fantastic idea! :) Imagine if we could multiply the TIA in software?

 

Here is a tripple TIA demo doing exactly what you described for a three way split screen:

Tripple_TIA_Demo.bin

 

I'm turning this into a game, and have another game under development that has just two TIA's handling a split screen.

 

Anyone who wants to build games with two or more TIA's can do so using display lists interrupts in Virtual World BASIC. The Atari home computers have been able to split GTIA up into virtual GTIA's this way since the 70's, many fantastic games utilize this functionality to great effect! :)

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Here is a tripple TIA demo doing exactly what you described for a three way split screen:

attachicon.gifTripple_TIA_Demo.bin

 

You're ROM does exactly what he described? Modified the Atari hardware to have 2 TIA chips driving different parts of the screen? I didn't realize Stella supported that kind of thing, letting you modify hardware via a ROM file ;-)

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You're ROM does exactly what he described? Modified the Atari hardware to have 2 TIA chips driving different parts of the screen? I didn't realize Stella supported that kind of thing, letting you modify hardware via a ROM file ;-)

 

Yes Virtual World BASIC supports display list interrupts that allow you to clone the TIA - one, two, three or even four TIA's can each drive a seperate split section of the display as Keatah described, here's more info and the BASIC source code for the demo:

 

http://atariage.com/forums/topic/251949-display-list-interrupt-demo/

 

Virtual World BASIC has a soft blitter chip that relatively repositions all of the sprites and the playfield whenever you move the camera.

 

You can create hardware in software, the blitter chip for the Amiga was initially implemented in software on the Apple II.

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A dual TIA system would be an interesting experiment, but I think it would be a non trivial task (and no, stacking 2 chips won't work...).

The point would be to mix the output of the two ICs to have double the object on screen without flicker.

 

The two TIAs need to be synchronized (an address must be mapped to strobe both "RSYNC" at the same time) and only TIA1 should have the SYNC and RDY pins connected (the first to the video output, the second to the CPU, so it can be halted by strobing the WSYNC register).

 

You could use the luma pins of the second TIA to select which output to display: if all three luma values of TIA2 are '0', then select TIA1, else select TIA2.

By setting the background color to "black" on TIA2, the output would be the one of TIA1, with all the sprites and playfield of TIA2 displayed on top of it. No hardware collision detection between sprites from different TIAs, and you cannot use the darker colors (with luma=0) on the second TIA.

Of course this requires a major rewiring of the board (or, better yet, a custom board) with extra logic to switch between the two video outputs and to address decode the second TIA which should be mapped in zero page to allow things like the "6 digit score" to work.

Since we're at it, why not wiring also the TIA2 input pins so we could have 8 simultaneous players paddle games? :D

Oh, and you should also find someone willing to program for that machine...

As for vertical split screen, as said by Thomas, the VCS can handle that just fine without modification. Just change and/or reposition the graphic object while you draw the screen. Almost all vcs games already do that to some extent.

Edited by alex_79
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Please contact Tod Frye. Supposedly, he put together a quick hardware project - to prove Atari's in-house engineering talent was better than GCC's - which used 4 TIAs in total so each TIA was only responsible for a quarter of the screen. Him and Jerry Jessop also supposedly put together a hybrid console that used the TIA - possibly just a single TIA at that - in conjunction with the ANTIC/GTIA that was not only backwards compatible with the 2600 and the 5200, but was also more powerful than GCC's 7800.

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