07642: truxton2: sprites flicker or disappear during certain (perhaps graphically busy) parts of the game

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
07642	Graphics	Major	Sometimes	May 5, 2020, 17:26	May 10, 2020, 08:57

Tester	mycophobia	View Status	Public	Platform	MAME (Official Binary)
Assigned To		Resolution	Open	OS	Linux (64-bit)
Status [?]	Acknowledged			Driver	toaplan/toaplan2.cpp
Version	0.220	Fixed in Version		Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	07642: truxton2: sprites flicker or disappear during certain (perhaps graphically busy) parts of the game
Description	https://www.twitch.tv/videos/612031359 https://www.twitch.tv/videos/612036141 see above links. sometimes, usually in late stage 5 or late stage 6 of the game, if there's a lot going on graphically then sprites will flicker or disappear. this does not happen in the original PCB, and seems to be a recent bug as I've played this game for over a year in MAME and don't recall it happening until recently. A fellow player thinks a change made in the following link (at the bottom of the page) could be the culprit: https://github.com/mamedev/mame/commit/feeb03c3ce0614adc5bb58485bf5211a414b80ed
Steps To Reproduce	Reach the spikes section of stage 6 (final stage, shown in video) or fight the stage 5 boss at full power. I've attached a savestate for the stage 5 boss fight with full power red weapon. I recommend turning on the invinicibility dipswitch and holding down the fire button to see the bug in action.
Additional Information
Github Commit

Flags
Regression Version
Affected Sets / Systems	truxton2

Attached Files	truxton2_stage5.zip (31,029 bytes) May 5, 2020, 17:26 Uploaded by mycophobia stage 5 boss fight full power

No.17611 hap Developer May 6, 2020, 12:53	More likely, cammy did this thing on several drivers: https://github.com/mamedev/mame/pull/6343
No.17616 jkm900 Tester May 8, 2020, 07:32	This issue is related to hardware level limitation, Actual PCB has similar problem. The limitation is need to verification.
No.17625 mycophobia Tester May 9, 2020, 16:12	from an original pcb recording: https://www.twitch.tv/videos/483994903 at 46:32 you can see the stage 5 boss fight at full power (like in the savestate I uploaded). there is a bit of flicker but i don't think it's as bad as in MAME currently. at 52:00 you can see the stage 6 spike section, where again there is a little bit of flicker but not as much as in current MAME. huge clumps of falling spikes don't disappear, none of the horizontal spikes disappear.
No.17626 MetalGod Senior Tester May 9, 2020, 16:43	This is fixed in mame 0.222 according to https://mameinfo.mameworld.info/
No.17628 hap Developer May 10, 2020, 08:57	It's also possible that MAME's sprite evaluation is the wrong way around. eg. you have max 80 sprites, game tries to place 100 sprites, and then: PCB: hide sprites 1-20 MAME: hide sprites 80-100 Another possibility is a status bit indicating sprite overflow, the game then reads this and shuffles the sprite ram if there was an overflow