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Thread: OVERDRIVE II

  1. #91
    Wildside Expert CrossBow's Avatar
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    Quote Originally Posted by Sik View Post
    Given that the refresh rate is what actually matters (the vblank time is much bigger in 50Hz than in 60Hz), yes you need to make it switch the refresh rate.
    Yes...I get that. My question was what is the process or mod required to switch a 60hz ntsc to 50hz? Again, using the 240p Test Suite, I can see that the region switch is working but the refresh is always 60hz regardless of the region. The 50hz to 60hz mod basically requires you to wire in the 53mhz crystal the NTSC units use, so is it the same for the ntsc; wiring in a different value crystal to drop it down to 50hz? If so..cool, but what crystal is needed?

  2. #92
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    Quote Originally Posted by CrossBow View Post
    Yes...I get that. My question was what is the process or mod required to switch a 60hz ntsc to 50hz? Again, using the 240p Test Suite, I can see that the region switch is working but the refresh is always 60hz regardless of the region.
    Do you have a full region switch setup that allows you to switch between all 3 valid regions or just a US/JP switch?

    Quote Originally Posted by CrossBow View Post
    The 50hz to 60hz mod basically requires you to wire in the 53mhz crystal the NTSC units use, so is it the same for the ntsc; wiring in a different value crystal to drop it down to 50hz?
    You don't need a different crystal to change the refresh rate in either direction. The different crystal is required to produce a correct color burst for the appropriate video standard. That only matters if you're using composite though. If you're using RGB, using the stock crystal is fine.

  3. #93
    Wildside Expert CrossBow's Avatar
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    [QUOTE=Mask of Destiny;791097]Do you have a full region switch setup that allows you to switch between all 3 valid regions or just a US/JP switch?

    Yes, I have full three way toggle between JPN in one position, US default in the Off switch position in the middle, and EUR to the second on position. Again, the 240p test suite immediately sees when I change this, but the video output is always at 60hz regardless. Interestingly, my TV would seem to indicate it can handle a 50hz signal because I'm able to use one of my s-video to HDMI converters to force it to output at 50hz and the TV will change accordingly and still show a clear picture.

    Now my Genesis is using an HD Retrovision cable to convert the RGB to component and that is going into the component input on my TV directly. But again I never see anything but a 60hz signal being generated.

    Before I got those cables I was using s-video out and had that going through my converter. But still it would never switch over to 50hz. Just seem to lock and output only at 60hz so I assumed another Mod was needed. And I've seen mention in other YT videos where people have a separate switch to select between 50 and 60hz and appear to be using a NA NTSC Genesis. Maybe they were using two position switches to be JPN/US and 50/60hz PAL?

  4. #94
    j_factor dislikes name! Master of Shinobi Flygon's Avatar
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    I'm a bit confused, that's... not how a region switch is suppose to work.

    The Mega Drive only has two regions, Japan and Export. Detecting European regions was a matter of checking both 50Hz and Export setting.

    How the heck does your region switch work?

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    I suppose the signal going to VDP that controls 50/60 got separated from what goes to the IO chip by whoever performed the mod. That way region checks of most games get fooled while VDP always stays in 50 or 60Hz.
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  6. #96
    Wildside Expert CrossBow's Avatar
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    Quote Originally Posted by Flygon View Post
    I'm a bit confused, that's... not how a region switch is suppose to work.

    The Mega Drive only has two regions, Japan and Export. Detecting European regions was a matter of checking both 50Hz and Export setting.

    How the heck does your region switch work?
    This is a US NTSC Genesis, I did the mod using the single on - off - on switch method. I believe it disconnects the US setting completely as it was found that without any region jumpers in place, the NTSC US consoles default to US. I then setup the switches for the EUR and JPN jumper positions. There are three ways to set the US system. Doing it the way I did only requires a single 3 way position switch.

    Used this process here on mine. I do know that I mentioned this in another thread, the but traces on my va2 didn't quite match what is listed on this website:

    https://mdpal60.net/wiki/megadrive/regionmod/start

  7. #97
    Master of Shinobi Sik's Avatar
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    Quote Originally Posted by Flygon View Post
    The Mega Drive only has two regions, Japan and Export. Detecting European regions was a matter of checking both 50Hz and Export setting.
    The video signal is considered part of the region as well (Sega's own region lockout code considers it to be part of the region, as do the docs).

    Japan is domestic + NTSC
    America is overseas + NTSC
    Europe is overseas + PAL

    Domestic + PAL is not considered a valid region.

    Quote Originally Posted by TmEE View Post
    I suppose the signal going to VDP that controls 50/60 got separated from what goes to the IO chip by whoever performed the mod. That way region checks of most games get fooled while VDP always stays in 50 or 60Hz.
    ...and why Konami games can't be fooled (they check the VDP instead of the region bits in the system register)

  8. #98
    Wildside Expert CrossBow's Avatar
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    Quote Originally Posted by Sik View Post
    The video signal is considered part of the region as well (Sega's own region lockout code considers it to be part of the region, as do the docs).

    Japan is domestic + NTSC
    America is overseas + NTSC
    Europe is overseas + PAL

    Domestic + PAL is not considered a valid region.
    Yes the page from Nico's site states that JPN + PAL is technically possible, but not practical. So I have to assume mine is wired wrong in some way. Again If I used the 240p test suite it will show JPN, US, and EUR when I flip it inside of that program. So I had assumed the switch must be working. And I found my previous post where I did state that some games would throw v-sync issues like rolling screen and such indicating that at least some titles are switching to 50hz mode perhaps. I will need to work it with more and test it more. But in the PAL or EUR setting on mine, the original Overdrive will get out of sync between the audio and video and eventually crashes 100% on the credits scroller with the robot shooting the names. Also reproducable in an emulator if you leave it set to 60hz. So..again something isn't switching it to 50hz mode as I would seem it should?

  9. #99
    Master of Shinobi Sik's Avatar
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    There are two places where the video signal shows up from the software viewpoint: in the system register (where both region bits are located) and the VDP status register (where the actual video signal being outputted will show up). It's technically possible to end up in a situation where they mismatch if things are not wired correctly (not sure if this can be done on every revision either), that will definitely confuse a lot of games as they often check the system register and assume it'll match the actual video signal. I believe Overdrive does this too (would have to check the code, the only tests I wrote had to do with checking against misemulation...).

    So huh, make sure you didn't overlook anything here. And if you wonder what they should get (video signal bit, overseas bit):

    Japan: 0 0
    America: 1 0
    Europe: 1 1

  10. #100
    Wildside Expert CrossBow's Avatar
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    Quote Originally Posted by Sik View Post
    There are two places where the video signal shows up from the software viewpoint: in the system register (where both region bits are located) and the VDP status register (where the actual video signal being outputted will show up). It's technically possible to end up in a situation where they mismatch if things are not wired correctly (not sure if this can be done on every revision either), that will definitely confuse a lot of games as they often check the system register and assume it'll match the actual video signal. I believe Overdrive does this too (would have to check the code, the only tests I wrote had to do with checking against misemulation...).

    So huh, make sure you didn't overlook anything here. And if you wonder what they should get (video signal bit, overseas bit):

    Japan: 0 0
    America: 1 0
    Europe: 1 1
    I will have to check things again. I can tell you that the original overdrive works the same way regardless of which way the switch is set. Overdrive II will always tell me that I need to be on a PAL console, so ODII somehow knows. A few other demos I have stored will also tell me they don't see the 50hz and warn me they may not work. Some do...most won't. I assumed just because the switch jumper settings are one way, that there was more to getting the 60hz to flip over to 50hz.

  11. #101
    Master of Shinobi Sik's Avatar
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    The first Overdrive was made compatible with NTSC in 1.1, so it doesn't care.

  12. #102
    Wildside Expert CrossBow's Avatar
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    I must not have that version of the OverDrive demo then. Again the one I have and have found online always crashes the genesis in the same place. I will need to look for this newer version. Thanks!

  13. #103
    Master of Shinobi Sik's Avatar
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    Wait a minute, right, it could still be affected by the mismatch between register and video signal >_> Go fix that, seriously =P

    Also you can tell apart Overdrive 1.0 from 1.1 not only because the former will only run in PAL (specifically, 50Hz), but also because the rotating 3D cube near the end has half the vertical resolution (in 1.1 it's full resolution).

  14. #104
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    Quote Originally Posted by Sik View Post
    ...and why Konami games can't be fooled (they check the VDP instead of the region bits in the system register)
    You can skip Bloodlines check by pressing start repeatedly after powering :-P
    I could with euro version on a 60hz console at least.

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