Double Dragon score-board jiggle [solved: region]

[Zelex]

I've seen this in a few emulators (including my own). Any ideas what the cause of that is? Pretty sure its done with SP0 hits, which occur on line 199, pixel 253/254 (alternating every other frame).

I'm thinking the problem might be that the scroll Y might be incremented a bit too late and the write isn't over-writing it properly? I have it increment at pixel 256?

[Zelex]

wiki says pixel 256, so maybe thats not it?

http://wiki.nesdev.com/w/index.php/The_ ... _scrolling

[Zelex]

Docs seem to imply that SP0 hits are delayed by 2 pixels, though I'm not sure how that would matter here, as 3 pixels per CPU clock. So it should be the same from the CPU's perspective, no?

[Dwedit]

How often are we talking about it jiggling? On decent emulators, I've seen it jiggle during high CPU usage times when it misses the sprite 0 hit.

[Zelex]

Jiggles quite a lot compared to fceux. I'd say once a second.

[Zelex]

so, I think your right. It doesn't get to the check for SP0 hit in time at all. So, maybe a vblank timing issue. Will investigate further.

[Zelex]

oh, nm. I think it was a PAL rom. I don't support PAL yet. That would be why the timing was all screwy.

geez, all that investigation and it was due to PAL.