PAL Demos In Color on 1702

[Paul Westphal]

So I built a NTSC 800xl with ultimate 1mb and stereo to run sweet euro demos. Some of the really good demos require both pal GTIA and ANTIC. Check. I left the NTSC Crystal in, and it looked like crap on my multi region LCD - runs in NTSC 3.58. So I tried it on a commodore 1702 and behold! It runs in color. Just have to adjust the horizontal. Normally pal won't run on a 1702 in color, but with this config it will. I just thought I would pass this on.

[Rybags]

So putting a PAL GTIA into an NTSC machine without supplying the 4.43 MHz clock to it's unique colourburst input pin must mean it just reverts to using the master clock input for colour generation then?

[Paul Westphal]

Apparently. I'm glad I stumbled upon this. My new LCD does true PAL, SECAM, NTSC 3.58 and 4.43, but looks crappy with this config. I use the 1702 for events.

[adam242]

Do games like Yoomp! and Pac Man Arcade run at the correct speed with this setup?

[papa_november]

The Commodore monitors and a lot of older, dumber tube TVs will happily accept NTSC-50. LCD monitors and multi-format standards-enforcing professional CRT monitors usually won't. Upscale devices tend not to like it either.

[Paul Westphal]

I will have to try them Adam. I primarily use this computer for demos and stereo music. It plays back ntsc .xex files no problem.

[adam242]

Cool. I'm guessing that they will if demos like Cyberpunk that check for a PAL GTIA will run correctly.

 

The reason I ask is that I've got a machine with a PAL ANTIC (but still has NTSC GTIA) that will run most Euro stuff fine, but games that do a $D014 check for PAL still see an NTSC machine and adjust themselves incorrectly. I didn't swap the GTIA because I thought the color signal would be wrong, but you've disproven that... Exciting stuff. I'm going to order a PAL GTIA and try this myself.

 

Now if only I could come up with a way to implement a switchable dual-ANTIC Atari.. But that's another topic.

Edited November 2, 2015 by adam242

[adam242]

Well, I'm pretty seriously bummed... My chips arrived today (thanks, Best!) and I attempted this tonight.

 

Didn't work in either the 800 or 1200XL I tried. Both booted up to a monochrome screen. Yes, I'm using a 1702. I tried with both the composite and Y/C inputs with both machines.

 

For the hell of it, I also tried them in my 800XL, just because that's what Paul initially made this work in... that machine must have died on the shelf, because it didn't do anything... still dead after swapping the NTSC chips back in. I thought about trying a 600XL, but I just quit while I was behind.

 

I'd REALLY like to get this to work in my Incognito 800... any hardware gurus have any thoughts?

[adam242]

Played around with this a little tonight on my 1200XL... If I bridge pins 16 and 28 (PAL and OSC inputs) on the PAL GTIA, I can get a color picture, it's just not right... the light blue boot-up screen has weird purple lines in it. It's hard to describe... I will try to get a picture tomorrow.

 

Paul, are the colors correct on your modified 800XL? That is, does it look the same as it did with the NTSC chips?

I wonder if those pins are already connected on the 800XL - maybe that's why it didn't initially work on my 800 or 1200XL.

[Paul Westphal]

The colors are a little off, the normal blue screen is a bit purple, but color is color. I don't see why this would not work on a 600xl as well. An 800 May not work. I could test it, I have extra PAL chips, but I'm sure it would work. Yes there are lines barely visible, but not bad.

[Paul Westphal]

Here are some pics.

[adam242]

Okay, I tried this same deal (PAL GTIA with pins 16 and 28 bridged) in my Incognito 800 today, with mixed results:

 

Memo Pad looks atrocious - purple screen with exaggerated scanlines:

 

PAL-only demo Cyberpunk and game Little Princess now run, but colors are wrong / look terrible:

 

River Raid colors are wrong, exaggerated scanlines:

 

Yoomp! and Pac-Man arcade now detect PAL and play at correct speed, but look bad and glitch badly:

 

 

I guess I could see using this occasionally to run demos at an event, but for a daily-use machine it's unacceptable to me. I'm going to go back to my hybrid PAL ANTIC / NTSC GTIA setup and just deal with the minor incompatibility issues. Most PAL stuff works fine that way, and the display is far better.

 

Not knocking you, Paul.. I appreciate the tip. It just doesn't work for me.