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Mario 3 converted IRQ fluctuation (random) please help!
http://forums.nesdev.com/viewtopic.php?f=10&t=16032
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Author:  infidelity [ Sun Jun 04, 2017 7:53 am ]
Post subject:  Mario 3 converted IRQ fluctuation (random) please help!

I've finally been getting around to testing my All-Stars NES project on my NES, I obtained my flasher from Hong Kong, and have been adjuasting the height & tearing of the Mario 3 IRQ. My All-Stars project is uses MMC5, so I had to convert the entire game from MMC3 to MMC5.

Anyways, I feel I've finally got the tearing looking as good as it can get, but I get this "random" fluctuation within the info bar at the bottom of the screen. I have no clue what to do, idk if I'm missing some sort of code, or if it's infact the adjustment of the tearing. I just don't know.

Here is a video of it in action. It only happens on real hardware, and on Nintendulator (the emulator I used to capture the glitch in action)

It happens at the 4 second mark of the video
https://www.youtube.com/watch?v=7Nt3m0le9sY&feature=youtu.be

Please, if anyone can explain what's happening and what I need to do, it would be huge, because it is this one thing that is stopping me from re-releasing my patch.

Thanks to all who view and offer suggestions!

Author:  infiniteneslives [ Sun Jun 04, 2017 8:04 am ]
Post subject:  Re: Mario 3 converted IRQ fluctuation (random) please help!

For MMC3, this is typically caused by noise on PPU A12, which requires a 220pF cap to clean up.

It's not fully known how MMC5 detects scanlines, so hard to be sure what's going on, or if it's actually a noise problem.

Author:  tokumaru [ Sun Jun 04, 2017 9:09 am ]
Post subject:  Re: Mario 3 converted IRQ fluctuation (random) please help!

Small variations can be explained by scroll changes that sometimes happen before the end of the scanline and sometimes after, due to the typical latency in handling IRQs on the NES. Since the PPU increments its vertical counter at the very beginning of hblank, the scroll change happening before or after it would cause the status bar to jump 1 scanline from time to time.

The jump in your video appears to be larger than 1 scanline though, so I'm not sure. If you do the scroll split earlier in the scanline, away from hblank, does this jump still happen?

Author:  infidelity [ Sun Jun 04, 2017 9:54 am ]
Post subject:  Re: Mario 3 converted IRQ fluctuation (random) please help!

I haven't attempted to reshift/relocate the code, it's pretty much within the same zone from its original state. I'll try to relocate the tear asm and see if that changes.

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