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Question about SNES sync drop

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This topic contains 5 replies, has 4 voices, and was last updated by  nullifer 3 months, 1 week ago.

Viewing 6 posts - 1 through 6 (of 6 total)
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  • #26211

    nullifer
    Participant

    Hello,

    I’ve seen that sometimes SNES are known to drop sync. But I’m not having the typical consistant drop out
    The sync drops are not often. like 1 time every 1-3hrs for a few seconds. But it’s a bit of an issue when trying to speedrun. (can invalidate run and such)

    However, I’m wondering if there is any option on the OSSC that I can adjust slightly to possibly eliminate these very ocassional sync drops?

    Would H-PLL precoast at a higher value help? also what exactly does it do, what does it affect turning it up?

    (my Scart cable also isn’t “amazing” quality either, could that cause it too?)

    #26219

    nmalinoski
    Participant

    To my knowledge, there’s nothing the OSSC can do; whatever sync errors it receives, it passes on.

    As for the problem itself (which happens with the NES as well), what happens is that, every other frame, the scanline preceding the first visible line gets cut short. That means that the horizontal sync pulses are not consistent, and a lot of contemporary hardware will have trouble accommodating it.

    I think you’ll either have to install a dejitter mod and then hope that doesn’t invalidate speedruns (should probably lobby for its acceptability moving forward), or you’ll need to do your speedruns on a display that can handle the SNES’s sync jitter, like a CRT, or perhaps a known-compatible plasma or LCD.

    #26223

    paulb_nl
    Participant

    Do you have a 1-CHIP SNES? If the OSSC itself loses sync then it could be another issue which happens with 1-CHIP SNES with Composite video or Luma sync cables.

    You can read about it here: https://www.videogameperfection.com/forums/topic/black-screen-in-yoshis-island-snes/

    #26225

    nullifer
    Participant

    I’m pretty sure this SNES is one of the earlier releases.
    It says 1991 on it, it’s very yellow, and Final Fantasy Mystic Quest debug says
    cpu ver.1
    ppu1 ver.1
    ppu2 ver.1
    I have a pretty cheap Scart cable, I have no clue which sync it’s using. I plan on getting a packapunch csync soon enough.

    I’ve seen other threads talking about adjust H-pll pre and post, and some others talking about vth might help out.
    I’d like to know what they actually do, help/hurt

    #26226

    BuckoA51
    Keymaster

    Adjusting H-pll pre and post sadly only hinders the SNES due to the jitter issue.

    #26228

    nullifer
    Participant

    And how about VTH?

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