08749: rezon: Severe slowdowns when there's a lot of sprites on screen

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
08749	Timing	Major	Always	Aug 28, 2023, 04:42	Sep 12, 2023, 16:11

Tester	Mamesick	View Status	Public	Platform	MAME (Official Binary)
Assigned To		Resolution	Open	OS	Windows 10/11 (64-bit)
Status [?]	Confirmed			Driver	seta/seta.cpp
Version	0.257	Fixed in Version		Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	08749: rezon: Severe slowdowns when there's a lot of sprites on screen
Description	The game exhibits severe slowdowns when there's a lot of action on the screen. This makes the game nearly unplayable at certain points. The frameskip is solid 100%. Regression is this commit: https://github.com/mamedev/mame/commit/9ff8931fa5067487f24067a3cadcb9095cee25cf where the IRQs for this game have been changed. Reverting it fixes the problem.
Steps To Reproduce	Just play the game for a while, better with Invincibility cheat enabled, due to the high difficulty of the game.
Additional Information
Github Commit

Flags
Regression Version	0.256
Affected Sets / Systems	rezon

Attached Files	0.255.avi.zip (3,108,800 bytes) Sep 12, 2023, 14:59 Uploaded by Mamesick Rezon 0.255 Level 2 - No slowdowns
Attached Files	0.258.avi.zip (3,578,388 bytes) Sep 12, 2023, 15:00 Uploaded by Mamesick Rezon 0.258 Level 2 - Big slowdowns

No.21714 AJR Developer Aug 28, 2023, 21:42	Currently Rezon is configured in MAME with a 60 Hz frame rate and 0 µs VBLANK period. The latter is definitely wrong and the former is likely considerably inaccurate. The correct video timings should be the same as those for numerous other Seta games on similar hardware; unfortunately, it doesn't look as if any of those have been measured on actual hardware either.
No.21716 Mamesick Senior Tester Aug 29, 2023, 04:29	What you say it's true and was already known before your commit. What I'm reporting here is simply that now (after your changes) things are worse than before. So the bug is confirmed and from my tests Rezon seems the only one affected in a visible way.
No.21749 hap Developer Sep 11, 2023, 22:01	I'm not on my desktop pc right now so can't check it on MAME. In this video I see slowdowns, is it worse on MAME?: If I had to guess, it acks the irq at the end of the irq routine, and if it overshoots the frame, it will have to wait until the next vblank.
No.21750 Mamesick Senior Tester Sep 12, 2023, 04:53	FWIW, this video is better to compare with current MAME. Just check level 2. In actual MAME slowdowns are worse. Before the AJR changes I'd say it's identical except for game speed which seems a little bit faster in MAME probably because refresh rate is not verified and set at the default 60 fps.
No.21751 hap Developer Sep 12, 2023, 09:48	I find it hard to notice much difference with slowdowns. I lowered refresh rate here: https://github.com/mamedev/mame/commit/bdab5c88153b5848f753aff79663670cc44b8ff8 It will also give the game a bit more time per frame to work on sprites. Did more fine tuning, and I think refresh rate matches daioh/zingzip (played video and MAME side by side at the ship introduction screens) https://github.com/mamedev/mame/commit/d08ff493b23409f42affb23cc291a2d71f6cec2e
No.21752 Mamesick Senior Tester Sep 12, 2023, 15:05	Thanks for taking care of this. FYI, I uploaded two videos (compressed with a very low bitrate to fit the max size of files upload here) to show the difference between 0.255 and current 0.258 about slowdowns. PCB videos are more similar to 0.255 than 0.258 in my opinion.
No.21753 hap Developer Sep 12, 2023, 15:59	"Thanks for taking care of this.", you mean the refresh changes fixed it? Sure, I can see the difference between your 2 files, it looks like you enabled cheats to let lots of sprites accumulate? But I can't easily see it when comparing normal gameplay of current MAME against those pcb videos. All of them have bad slowdowns.
No.21754 Mamesick Senior Tester Sep 12, 2023, 16:11	Yes, I enabled "Invincibility" to pass through the enemies. I have no time to compile MAME now, though with the sliders changing the refresh rate in 0.258 improves things. Not completely, though. I don't want to ask or force you to revert AJR changes for Rezon. Though in my opinion you should have a look at current implementation. Peace.