06067: 64street, 64streetj: 64th Street - missing background graphics interaction

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
06067	Graphics	Minor	Always	Nov 7, 2015, 14:44	Dec 9, 2015, 00:52

Tester	system11	View Status	Public	Platform	MAME (Official Binary)
Assigned To	Kale	Resolution	Fixed	OS	Windows Vista/7/8 (64-bit)
Status [?]	Resolved			Driver	jaleco/megasys1.cpp
Version	0.167	Fixed in Version	0.169	Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	06067: 64street, 64streetj: 64th Street - missing background graphics interaction
Description	Long standing bug I can't actually see a report for. In 64th Street the majority of the backgrounds can be destroyed by throwing enemies into them, half or more of this is missing in MAME, is this anything to do with the priority PROM I dumped a while back - presumably this could be caused if there was an overlay layer appearing behind the normal backgrounds or in front? Have uploaded a poor quality video which shows this in action:
Steps To Reproduce	Every game, throw an enemy into background elements.
Additional Information
Github Commit

Flags	Verified with Original
Regression Version
Affected Sets / Systems	64street, 64streetj

Attached Files

No.12147 Mamesick Senior Tester Nov 8, 2015, 20:27	FWIW, it was the same behaviour also before you dumped the priority PROM and the game used the hand-made priority structures which I personally fixed for this game at least 10 years ago. So my guess is that there's something unemulated in video hardware, probably a sort of sprites-bg collisions detection register that if enabled starts to draw the modified bg layer. On a side note, the only game that still uses the hand-made priority method is Chimera Beast. It would be great have that PROM dumped too.
No.12232 Kale Developer Dec 9, 2015, 00:52	Breakable stuff is writing to a VRAM mirror area.

No.12147

Mamesick

Senior Tester

Nov 8, 2015, 20:27

FWIW, it was the same behaviour also before you dumped the priority PROM and the game used the hand-made priority structures which I personally fixed for this game at least 10 years ago. So my guess is that there's something unemulated in video hardware, probably a sort of sprites-bg collisions detection register that if enabled starts to draw the modified bg layer.
On a side note, the only game that still uses the hand-made priority method is Chimera Beast. It would be great have that PROM dumped too.

No.12232

Kale

Developer

Dec 9, 2015, 00:52

Breakable stuff is writing to a VRAM mirror area.