Pixel Garbage in Wolfchild (Sega CD)

[Former user]

Original issue 356 created by gora.patrick on 2013-08-09T17:23:15.000Z:

What steps will reproduce the problem?
1. at the beginning of level 1 just jump right at the beginning and you'll see a pixel garbage line at the top of the screen, which wasn't there before.

What version of the emulator are you using (official, SVN revision,...)?

the latest version that comes with retroarch 0.9.9.4

Please provide any additional information below (Emulator settings, Console
setting,...)

playing on OUYA, Game is NTSC

[Former user]

Comment # 1 originally posted by gora.patrick on 2013-08-10T12:21:43.000Z:

seems only to affect the US Version, as everything is fine with my PAL Version.

[Former user]

Comment # 2 originally posted by ekeeke31 on 2013-08-16T00:29:28.000Z:

by "which wasn't there before", do you mean that the bug did not occur in a previous version of the emulator ?

[Former user]

Comment # 3 originally posted by gora.patrick on 2013-08-16T08:50:20.000Z:

yup, at least i didn't recognized it.

[Former user]

Comment # 4 originally posted by ekeeke31 on 2013-08-20T20:32:46.000Z:

I just checked and :

1) it's not constantly happening when you jump, most of the time but not always so it's easy not to notice it

2) it only happens in that part, when standing on the top platform

3) it happens in Fusion / Gens too

From debugging, when jumping, the game do some VRAM updates during active screen, which is the cause of the pixel garbage.

It's probably a bug in original game with the way scrolling is handled at the top of the screen (only seen when jumping from the top platform at the start) and most likely happens on real hardware as well (if it was caused by emlator inaccuracy, you would have an entire line of garbage, not a bunch of pixels).

It does not happen on PAL system because VBLANK has more time and those extra VRAM writes are completed before active display starts.