Question about SNES PPU, NTSC vs PAL - video encoder ?

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Ziggy587
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Question about SNES PPU, NTSC vs PAL - video encoder ?

Post by Ziggy587 »

From everything I've read, I've always thought (or incorrectly assumed) that the SNES PPU was the same in all console. The PPU could be set to output PAL 50 Hz or NTSC 60 Hz.

After mentioning on another forum that I wanted to use a PAL SNES as an NTSC SNES (I'm in the USA), some one warned me that I would have problems doing that. He said that running a PAL SNES in 60Hz would cause some kind of problem, and linked a YouTube video where the screen flickers when Super Mario World is played in 60Hz (among other examples).

What I don't know is if these problems are caused from running a PAL game in 60Hz on a PAL TV, or if there's something else going on that I don't understand. I was planning on hardwiring my PAL SNES to output 60Hz (no switches). If I do that, and fix the lockout, will I effectively have an NTSC SNES? Or will it be outputting a PAL 60Hz video?

As always, thanks for the help!

edit: Fixed first link to correct URL
Last edited by Ziggy587 on Mon Jan 21, 2013 9:28 pm, edited 1 time in total.
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mikejmoffitt
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Re: Question about SNES PPU, NTSC vs PAL

Post by mikejmoffitt »

I don't know what significance can be attached to that video... it looks as though he is hot-swapping between 50hz and 60hz. I would expect many games make note of the intended speed upon bootup and don't try to determine it all the time, so the adjustments it is doing for 50hz while in 60hz mode could cause issues.

That screen flickering has nothing to do with the video signal itself. PAL and NTSC only come in to play at the encoding stage of the video and don't bear a relation to the PPU as far as I know.
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Ziggy587
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Re: Question about SNES PPU, NTSC vs PAL

Post by Ziggy587 »

So am I correct? The PPU is the same in an NTSC and PAL console? If I change the PPU pin(s) from +5v to ground, it'll be the same as an NTSC PPU?
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Ziggy587
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Re: Question about SNES PPU, NTSC vs PAL

Post by Ziggy587 »

OK, so I got around to doing this. My PAL SNES is the 1chip version with combined CPU and PPUs. On my PAL SNES, I lifted pin 111 of the S-CPUN and connected it to ground. I swapped X1 with the crystal from an NTSC SNES. I also swapped the lockout chip with one from an NTSC SNES. When I tested it with an NTSC-U cart (Super Mario World) it worked but the colors are all wrong. The picture is very red. The image is stable, so I know the 60Hz mod took, but the colors are way wrong.

So some I did some Googles, and I'm pretty sure I found the answer, but I can't figure out exactly WHAT I need to do.

I knew of the Super CIC mod for the 1chip on the sd2snes site, so I pulled that up first.

http://sd2snes.de/files/1chip-5060.pdf

If you look in the bottom right, it says to lift pin 9 on the encoder for "true NTSC/PAL signal". So naturally, I just need to find out what I need to do to that pin! But that's where the problem is. I can't find any info on it. There's this thread...

http://nfggames.com/forum2/index.php?topic=3525.0

...but all the links are dead. There's a pinout for the S-RGB encoder, and sure enough pin 9 is labeled "NT/PAL" but I still have no idea what to do with that pin. Is it a 5v/GND thing like the PPU pin? Or is it something else?
lidnariq
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Re: Question about SNES PPU, NTSC vs PAL

Post by lidnariq »

Ziggy587 wrote:There's a pinout for the S-RGB encoder, and sure enough pin 9 is labeled "NT/PAL" but I still have no idea what to do with that pin. Is it a 5v/GND thing like the PPU pin? Or is it something else?
This is only guesswork, but it is most likely NTSC/PAL = 5V/Gnd, and specify whether the encoding is the standard NTSC "colorburst is -U", or PAL "colorburst alternates between -U-V and -U+V".
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Ziggy587
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Re: Question about SNES PPU, NTSC vs PAL - video encoder ?

Post by Ziggy587 »

So looking at the encoder in my PAL SNES, pin 9 is connected to pin 11. They are both ground. I took a look at the encoder inside my NTSC SNES mini, pin 9 is 5v. So I'm assuming that all I have to do is lift pin 9 in my PAL SNES and connect it to 5v and all will be good.
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Re: Question about SNES PPU, NTSC vs PAL - video encoder ?

Post by tepples »

There are technically three differences between NTSC and PAL signals, apart from thevCIC difference: 50/60, inversion of V phase per line, and the subcarrier frequency. If you invert V on every second line and add V to burst (apparently pin 9), but you leave it at 60 and near-NTSC subcarrier, you get Brazil's PAL/M. What controls each component?
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Ziggy587
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Re: Question about SNES PPU, NTSC vs PAL - video encoder ?

Post by Ziggy587 »

OK, so I've lifted pin 9 on the video encoder and connected it to 5v and now everything appears to be correct. Though I wish I could have a look at the datasheet for the S-RGB just to be sure there isn't anything else.
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keropi
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Re: Question about SNES PPU, NTSC vs PAL - video encoder ?

Post by keropi »

I am sure it's fine, S-RGB pin9 is also used on the 50/60hz switch, it's either gnd or vcc ...
have a look here , there are pics and info from when I modded my 1st 1CHIP snes (that died btw...), I never knew the picture quality would be so much better :)
http://www.assemblergames.com/forums/sh ... help/page2
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l_oliveira
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Re: Question about SNES PPU, NTSC vs PAL - video encoder ?

Post by l_oliveira »

I know this is an old topic but here it goes anyway:

The pin on the encoder chip will affect the "format" of the encoded color carrier burst that will be generated by the encoder.

Tinkering around you can get:

PAL 60
NTSC 50

PAL-M (60hz but color carrier is transmitted in PAL format and at an frequency near as the one used by NTSC so aerial tuners and transmitters are compatible, carrier = 3.575611Mhz)


What glitches the games (as per youtube video) is the 50/60hz switching.

I am familiar with the NTSC/PAL thing because here in Brazil most consoles were brought in through smuggling so it was VERY COMMON for me and other repair shops to offer an service called "transcodification" which would change the color encoder to output PAL-M instead of NTSC.

About 90% of the videogame hardware here are either for USA/Canada or Japan.
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