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ID Category [?] Severity [?] Reproducibility Date Submitted Last Update
07965 Graphics Major Always 12 days ago 12 days ago
Tester kmg View Status Public Platform MAME (Self-compiled)
Assigned To Resolution Open OS MacOS X
Status [?] Confirmed Driver sms.cpp
Version 0.231 Fixed in Version Build 64-bit
Fixed in Git Commit Github Pull Request #
Summary MESS-specific 07965: gamegear [ddragon, ddragonp]: Corrupt background tiles
Description Double Dragon (and prototype clone) start with working graphics. As soon as you start a game from the title screen the background graphics become completely corrupt. Foreground sprites seem to be fine. See images.
Steps To Reproduce mame gamegear ddragon, and then simply start the game
Additional Information
Github Commit
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Regression Version
Affected Sets / Systems gamegear [ddragon, ddragonp]
Attached Files
png file icon intertitle1.png (3,364 bytes) 12 days ago Uploaded by kmg
kmg
png file icon level1.png (6,706 bytes) 12 days ago Uploaded by kmg
kmg
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Notes
2
User avatar
No.18799
Tafoid
Administrator
12 days ago
This is an odd one.
It work/loads graphics fine if loaded picker style-cart c:\location\of\cart\ddragon.zip as far back as I could test.
I guess the issue would be finding the difference in what happens from softlist load vs. picker loading.
User avatar
No.18801
kmg
Tester
12 days ago
edited on: 12 days ago
It wouldn't even have occurred to me to test it outside the software list, but this was the perfect clue. I figured it was just some VDP issue, but it turned out to be a simple bank switching problem. Thanks Tafoid!

When loading with -cart the sega8 slot code allocates 32K of RAM because it has no way of knowing in advance if a game has any on chip. The softlist allocates none. I verified in the debugger that the game writes to $FFFC (RAM bank select) when you start a new game (but not before, hence the working title screen). Fix is in https://github.com/mamedev/mame/pull/8027/commits/f2392ffcf666f7707310bea22628e9d787c17a06 though I'd like it if someone could confirm these carts actually have 8K of RAM (and not more)? I think this guess is correct. One, it seems only GG carts with battery backup ever had more than 8K? And two, MAME only had data in the first 8K of the 32K nvram files it created when running the games via -cart.