Interesting PAL/NTSC famiclone

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krzysiobal
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Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland

Interesting PAL/NTSC famiclone

Post by krzysiobal » Tue Apr 18, 2017 3:03 pm

I got interesting famiclone, with a lot of weird jumpers (it does not have any built-in games). It is powered by single 26.601712 MHZ crystal.

Image Image

1. Closing or opening jumpers WRAM, VRAM, P1Y3/A5 does not change anything.
2. Jumpers OPT1, OPT2, OPT3 are quite interesting.
- When none of them are closed, console generates PAL video (the same as on Dendy or other famiclones - games which needs true PAL like Asterix does not work)
Image

- When OPT2 is closed, console generates NTSC video - the sound is a bit faster and the video aspect is not letter box as in PAL.
Image
To be honest, I dont know if it is real NTSC or PAL with 60HZ and less scanlines, because my TV can synchronize to this video when video source on TV is set as: PAL or as NTSC (when I plug in console which generates true NTSC on 21.417 MHZ crystal and UA6528&UA6527, when TV video source is set as PAL, the video cannot be vertically synchronized). So maybe this is not real NTSC?
The image shakes a little bit, which is vissible on the edges:
Image

-When OPT3 is closed, the console generates gray scale PAL video, although when TV in auto mode, the image is switching. When I force it to secam, it is still gray scale but more stable.
Here is comparision when TV is set to SECAM and OPT3 is closed or open - the image differs a bit on straight vertical edges.
Image

- When OPT1 is closed, the sound is like 150% faster, TV loses sync (althought something is displayed). Maybe it is for speeding-up game or when replacing crystal with 21 MHZ, it would generate true NTSC?
Image

All this playing with jumpers can be done on-the-fly, the game does not crash at all! :)

lidnariq
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Re: Interesting PAL/NTSC famiclone

Post by lidnariq » Tue Apr 18, 2017 4:01 pm

krzysiobal wrote:To be honest, I dont know if it is real NTSC or PAL with 60HZ and less scanlines, because my TV can synchronize to this video when video source on TV is set as: PAL or as NTSC (when I plug in console which generates true NTSC on 21.417 MHZ crystal and UA6528&UA6527, when TV video source is set as PAL, the video cannot be vertically synchronized). So maybe this is not real NTSC?
Pretty certain that's PAL60, because the chroma-into-luma crosstalk along vertical edges has a 6-scanline repeat pattern instead of 3-scanline.
Maybe it is for speeding-up game or when replacing crystal with 21 MHZ, it would generate true NTSC?
Seems almost guaranteed...

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tokumaru
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Re: Interesting PAL/NTSC famiclone

Post by tokumaru » Tue Apr 18, 2017 4:08 pm

Is PAL60 different from PAL-M?

lidnariq
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Location: Seattle

Re: Interesting PAL/NTSC famiclone

Post by lidnariq » Tue Apr 18, 2017 5:08 pm

Yes. PAL-60 is the standard 4.433MHz colorburst frequency instead of PAL-M's 3.575MHz.

krzysiobal
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Joined: Sun Jun 12, 2011 12:06 pm
Location: Poland

Re: Interesting PAL/NTSC famiclone

Post by krzysiobal » Tue Apr 18, 2017 6:16 pm

Now time for next part of test - results are even more funny.
I switched the crystal from 26.601712 MHz to 21.47727 MHz.

-When no jumpers are present, the sound is about 50% slower and the video cannot synchronize (just like @26.601712MHz and OPT1 closed)

- When OPT1 is closed, I got grayscale PAL image.
Image

- When OPT1 + OPT3 are closed, no difference like above.

- When OPT1 + OPT2 are closed, I got coloued NTSC image. This time it appears to be true NTSC because TV can sync with it only when in NTSC mode. Hovewer, the colours are FAKE and there is weird checkboard pattern on the whole image. But the image is very stable.

Image Image Image

- When OPT1 + OPT2 + OPT3 are closed, I got perfect NTSC Image. This time colours are valid and no checkboard patter. However, music started sound weird (like 1 channel was cut off):
Image Image

So I suspect:
*OPT1 - is responsible for diving crystal
*OPT2 - turns between PAL/NTSC
*OPT3 - color phase or what?

lidnariq
Posts: 9689
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Interesting PAL/NTSC famiclone

Post by lidnariq » Tue Apr 18, 2017 7:48 pm

krzysiobal wrote:- When OPT1 + OPT2 are closed, I got coloued NTSC image. This time it appears to be true NTSC because TV can sync with it only when in NTSC mode. Hovewer, the colours are FAKE and there is weird checkboard pattern on the whole image. But the image is very stable.
That almost looks like it's just the U component (or maaaaybe the I component?) of the video? That might be an artifact of the palettes in the sample games, though.

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