03909: shinobi: In stage 3-2, there is a noticeable stutter in scrolling horizontally

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
03909	Graphics	Minor	Always	Jun 30, 2010, 16:02	Jun 30, 2010, 16:04

Tester	-Misc Reporters-	View Status	Public	Platform
Assigned To		Resolution	Bugs That Aren't Bugs	OS
Status [?]	Resolved			Driver	sega/segas16a.cpp
Version	N/A	Fixed in Version		Build
		Fixed in Git Commit		Github Pull Request #

Summary	03909: shinobi: In stage 3-2, there is a noticeable stutter in scrolling horizontally
Description	In stage 3-2, there is a noticeable stutter in scrolling horizontally. This appears to be the only set which does this on this particular stage. The parent is the "unprotected" version. shinobi1 (FD1094) and other bootlegs all have a smooth scrolling screen in all directions in this level.
Steps To Reproduce
Additional Information	Reported by edcosta/Rogerio: http://www.mameworld.info/ubbthreads/showthreaded.php?Cat=&Number=224827 Report from Junoman: Looks like it's a bug in the original code. (BTANB) The game code is identical with the exception of removal of 4 mov 0,$f00X and a simplified tile conversion routine which is only used in stage 3-2. I've only looked at the code but I'm assuming they changed the data at assembly/build time instead of at run time in the newer FD1094 version. The stuttering is caused by the extra cpu cycles used in the conversion routine pushing the game over the vblank interrupt period. (making it skip a video frame) Putting the new code in the stuttering version gets a corrupt display so it's not just an optimization.
Github Commit

Flags	Verified with Code
Regression Version
Affected Sets / Systems	shinobi

Attached Files