Swapping MD Master Clock Generator

Discussion in 'General Sega Discussion' started by Oerg866, Dec 25, 2008.

  1. Hey there.

    I've recently acquired a (broken) japanese MD1. A while ago I got to know that with swapping some master clock thing you can get the normal PAL console to output correct signal on 60Hz, so that you don't necessarily need an RGB Scart cable.

    I ask the techs here to tell me what I need to do, please.

    bai
    oerg866

    <!--quoteo(post=214975:date=Aug 9 2008, 01:09 PM:name=TmEE)--><div class='quotetop'>QUOTE (TmEE @ Aug 9 2008, 01:09 PM) [​IMG]

    [​IMG]
     
  2. GerbilSoft

    GerbilSoft

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    That would be the oscillator. If you look on the board, you'll see a small rectangular all-silver chip. That's the oscillator. (It's right next to the Z80.)
     
  3. They're exactly the same on both machines though.

    Well not exactly, but they both have 53,6931MHZ

    EDIT: I was wrong. The PAL one was 53,203MHZ
     
  4. Swapped and FUCK YES:

    [​IMG]

    Screw you all! :D

    And thanks GerbilSoft ;)
     
  5. Moogle!

    Moogle!

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    What would happen if you put one in there that ran at double the clock speed?
     
  6. GerbilSoft

    GerbilSoft

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    Everything would fuck up horribly. All the frequencies are derived from the main oscillator, so you'd affect the MC68000, the Z80, the YM2612, the NTSC/PAL encoder, and other components. You'd probably fry some stuff, too.
     
  7. Moogle!

    Moogle!

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    I figured as much. But that leads me to a new question. Don't NTSC and PAL hardwares have (minutely) different speed CPUs in them? Why did this not throw it slightly out of whack?
     
  8. Sik

    Sik

    Sik is pronounced as "seek", not as "sick". Tech Member
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    being an asshole =P
    Yup =P

    NTSC 68k speed: 7.67MHz
    PAL 68k speed: 7.60MHz
     
  9. GerbilSoft

    GerbilSoft

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    I believe the CPUs are identical. The reason they run at different frequencies is because of the different oscillator.

    NTSC master frequency: 53.6931 MHz
    53.6931 MHz / 15 = 3.57954 MHz (NTSC color subcarrier frequency)
    53.6931 MHz / 7 = 7.67044 MHz (MC68000 frequency)

    PAL master frequency: 53.203 MHz
    53.203 MHz / 15 = 3.54686 MHz (this is why you can't get NTSC color from a PAL console)
    53.203 MHz / 7 = 7.60043 MHz (MC68000 frequency)
     
  10. Ah. Good to know the details.

    Though, I've been wondering why you could get color via an RGB cable.
     
  11. GerbilSoft

    GerbilSoft

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    RGB doesn't use any NTSC or PAL modulation. The only thing that changes with the different clock ICs is the horizontal sync, which is usually in the tolerance range for 15 kHz RGB monitors.
     
  12. Wait. does that mean I could hook this thing up to a commodore 1084 monitor?
     
  13. GerbilSoft

    GerbilSoft

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    Depends on the specific 1084. Some only support digital RGB (e.g. CGA), while others support analog RGB. If yours supports analog RGB, then yes, you can connect the MD to the 1084. Look up the pinouts for the MD A/V port and the 1084's RGB port.
     
  14. TmEE

    TmEE

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    T-04YBSC-A !
    I have both PAL and NTSC master clocks in my MD2 for whenever I need true PAL or NTSC. I recently found out that my TV accepts NTSC too when the subcarrier is correct, and I have to say that NTSC composite looks worse than PAL... much more subcarrier artifacts, even poorer colors... ugh. RGB is total bliss compared to these. Amiga monitor would be a better option than C64 one ?
     
  15. No. They're not really different.