PAL SNES not 1-chip replace oscillator

Discussion in 'Modding and Hacking - Consoles and Electronics' started by Kagigod, Feb 17, 2017.

  1. Kagigod

    Kagigod Member

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    Hello,
    I tried to search for this but couldn't find a concret answer.

    I have a PAL SNES in which I did this mod 60hz and disable CIC chip mod:


    Everything is working great and the mod is super clean, but the console has a slight out of spec refresh rate when running in 60hz, which causes some sync problems in my TV when using the Framemeister. Is it possible to change the PAL crystal oscillator and use an NTSC one? Will the console then work just as an NTSC console when in 60hz mode?

    Also, I seem to be unable to find the 21,47727 MHz crystal in europe, preferably in Spain, can anyone help me find it, please?

    Thanks
     
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  2. Bearking

    Bearking Konsolkongen

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    skyway1985 likes this.
  3. skyway1985

    skyway1985 Enthusiastic Member

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    as bearking said, get the Xtal from Bad_Ad84, you are absolutley correct BTW just swap the crystal OR piggy back it with a switch so you can switch back and forth.
     
  4. borti4938

    borti4938 Robust Member

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    DON'T do that!!! It's more complicated than you might think.

    On a 3Chip-SNES you have the S-CLK on board, which makes the master clock of ~21.281MHz out of the ~17.734MHz (multiplied with 6/5) among some other clocks... (Other clocks generated here are the carrier of the composite video signal and clocks for CIC-lock and CIC-key.)
    So if you replace the ~17.734MHz crystal with a ~21.477MHz without changing anything else, your SNES won't start anymore as the system clock is now ~25.772MHz. (Also the carrier of the composite video signal will far away from NTSC specs)
     
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  5. Ergot_Cholera

    Ergot_Cholera Flaccid Member

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    Take note of Borti, he is SNES genius.
     
  6. skyway1985

    skyway1985 Enthusiastic Member

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    yea he is lol @borti4938 is there seperate Xtals for all of them?
     
  7. Kagigod

    Kagigod Member

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    Ouch, I feared there was something like that, as the SuperCIC mod has a crystal switch for the 1-chip but not for the 3 chip. I guess there's really nothing I can do here besides finding a 1chip or a Super Famicom, right?
     
  8. zzattack

    zzattack Spirited Member

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    You can resolve most of the sync issues by restoring c-sync and using a NTSC RGB cable.
     
  9. Bearking

    Bearking Konsolkongen

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    He's talking about getting the system to output at the exact refresh rate as the NTSC-systems. Even with the "60Hz" mod on a PAL system this will differ slightly, resulting in stutter on some displays or upscalers like the XRGB-mini. The same is true for the Mega Drive and Saturn and probably other too, but at least these systems can be corrected by using a Dual Frequency Oscillator mod :)
     
  10. zzattack

    zzattack Spirited Member

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    I'm not saying restoring C-Sync on PAL systems will magically cause it to output proper clocks for 60Hz refresh rate ;)
    The point is rather that getting actual c-sync instead of the composite-based signal obtained with a sync-stripper like the LM1881 helps a lot with scalers like you mentioned.
     
  11. Bearking

    Bearking Konsolkongen

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    That's true :)
     
  12. borti4938

    borti4938 Robust Member

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    I guess his problem is something like that:

    [​IMG]
    60Hz modded PAL Mega Drive with incorrect timings

    [​IMG]
    60Hz modded PAL Mega Drive with correct timings
    Note that the incorrect timings also causes that 'black' is a little bit grey on the Framemeister...


    Inside the S-CPUN (the big IC which gives the name to the 1Chip) there is a S-CLK like circuit inside. All clocks are generated here according to the value on pin 111 (GND for 60Hz mode and 5V for 50Hz mode). That's why you need the change the value of X1 accordingly.

    I believe, it should be possible to get NTSC timing out of a PAL SNES with 60Hz modded. If you are really really really interested in, I will look on my bare boards to give you some notes what you have to do... A static solution should be easier to achieve compared to a switchable one.
     
    Last edited: Feb 21, 2017
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  13. Kagigod

    Kagigod Member

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    I would very much appreciate this if you can find the time for it :) I guess a static solution will be fine, as almost 100% of the time the console is in 60hz mode. What will happen if I run the console in 50hz mode with the NTSC timings fixed? A slight out of spec PAL timing or the console won't boot at all?

    Thanks a lot for your help
     
  14. borti4938

    borti4938 Robust Member

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    Fine! ... give me a couple of days ;)
     
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  15. rogerhanin2002

    rogerhanin2002 Active Member

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    Bump post for a before site crash thread..

    Any news on this static solution ??
    Cause i'm very interested too.

    Thanks in advance.
     
    Last edited: Sep 4, 2017
  16. Harrumph

    Harrumph Newly Registered

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    Another bump, as I am also interested in this question.

    Did you reach any conclusion borti?

    I’m not at all competent in electronics, but could the 6/5 clock multiplier be reversed by somehow putting a 5/6 multiplier on the output of an NTSC crystal? Could the dual frequency oscillator (DFO) be employed perhaps (I remember reading that it can be custom programmed)?
     
  17. Kagigod

    Kagigod Member

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    Maybe this sync jitter mod in the works could be of use for this?
     

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