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Grevle

Pal Atari 800xl with Ntsc GTIA or Antic ?

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Is there any way to "trick" the PAL Atari 800xl to show the NTSC aspect (image fills the screen better on Pal crt tv with NTSC aspect).

 

Wonder what happens if i put a NTSC GTIA or NTSC ANTIC in a PAL Atari 800xl ?

 

Will it show the NTSC aspect ? or will issues like timing or other stuff mess it up ?

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Antic decides whether the screen is 50 or 60 FPS with 312 or 262 scanlines - those pairings aren't interchangable e.g. can't have 60 FPS with 312 lines.

 

GTIA decides on the colour encoding - Pal GTIA have the second crystal which is used for the 4.43 MHz colourburst, NTSC GTIA generates it from the same crystal the CPU uses.

GTIA also has the PAL register which software can use to determine what system is being run on.

 

Putting "foreign" chips into your machine can cause more problems than it solves - one of which being many TVs will refuse to show colour.

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Is there any way to "trick" the PAL Atari 800xl to show the NTSC aspect (image fills the screen better on Pal crt tv with NTSC aspect).

No. Your best option is to pull up the screen on an analog monitor.

 

Wonder what happens if i put a NTSC GTIA or NTSC ANTIC in a PAL Atari 800xl ?

 

Will it show the NTSC aspect ? or will issues like timing or other stuff mess it up ?

 

As far as antic is concerned, this will change the numbers of lines on the screen, though the frequency will be off since the base frequency is not exactly the NTSC color frequency. For GTIA, without further modifications, color will be missing since PAL uses a different color clock. For NTSC, the color carrier is half the pixel clock, but PAL uses 5/4 of the NTSC clock, avoiding the typical NTSC artifacts.

 

If you want to convert a PAL Atari to a NTSC, you not only need to exchange ANTIC and GTIA, you also need to change the base crystal, and you need to remove the 5/4 multiplier generating the color clock on PAL Ataris. This unit consists basically of two 7474 flip flops implementing a 1/4 frequency divider and a crystal running at the color carrier frequency which is synchronized by the output of the flip-flops.

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Thanks for you answers, I dont want to convert PAL Atari to NTSC since i got both Pal And NTSC Ataris, i wanted to fill screen better on Crt Tv with Pal Ataris, Yes you right, The best option is to have Crt screen with the ability to strech the screen (service menu) to achieve that.

Edited by Grevle

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I was just testing an NTSC ANTIC in my PAL 800XL - It stretches the screen vertically compared to the PAL ANTIC.

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