02160: mk2r14: Pressing P2 button six causes the game to hang

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
02160	DIP/Input	Critical (emulation)	Always	Aug 24, 2008, 22:37	Jan 5, 2015, 11:44

Tester	rittwage	View Status	Public	Platform	MAME (Official Binary)
Assigned To		Resolution	Open	OS
Status [?]	Confirmed			Driver	midway/midtunit.cpp
Version	0.127	Fixed in Version		Build	Normal
		Fixed in Git Commit		Github Pull Request #

Summary	02160: mk2r14: Pressing P2 button six causes the game to hang
Description	MAME crashes when playing mk2r14 when pressing anything mapped as button 6.
Steps To Reproduce	Map P2 button 6 to anything (it's not mapped by default) in general config, not game config, because technically MK2 has no button 6. Press it at any time and MAME crashes with -------------------------------------------------------------------- Exception at EIP=00B83719: ACCESS VIOLATION While attempting to read memory at EC3B00A0
Additional Information
Github Commit

Flags
Regression Version
Affected Sets / Systems	mk2r14

Attached Files	mk2.png (288,392 bytes) May 21, 2009, 00:41
Attached Files	mk3.png (349,645 bytes) May 21, 2009, 00:42

No.02210 rittwage Tester Aug 24, 2008, 23:03	Note this only happens with that specific ROM version (1.4). Other MK2 rom revisions do not crash this way, nor do the other MK drivers (that I could find).
No.03037 Luigi30 Tester Nov 13, 2008, 01:04	If you press the button in the switch test, it doesn't crash until you exit switch test.
No.03650 etabeta Developer Jan 26, 2009, 09:32 edited on: Jan 26, 2009, 09:33	in this set, when you press P2 button 6, game code jumps to FF9D04E0 and it remains there (in gdb it doesn't even crash, it simply stays there forever) other sets do not reach that location (neither when you press P2 button 6 or elsewhere) could it be an original bug or a bad dump?
No.03694 Luigi30 Tester Jan 29, 2009, 20:08	There's also a JA FF9D04E0 at FF9CF620 but it doesn't get triggered by pressing P2 button 6.
No.04406 Tafoid Administrator May 21, 2009, 00:40 edited on: May 21, 2009, 00:44	Perhaps I'm missing the obvious, but in my research and recollection of this game, there were only 5 action per side for Mortal Kombat II. The buttons for MK II were Low Punch, High Punch, Low Kick, High Kick and Block and of course, start. A wired up #6 button makes no sense and it's no wonder there is not code to handle it. The Diagnostics also, only outlay 5 player buttons per side, not 6. In short, the #6 button on MK II should not exist in the emulation. Mortal Kombat 3, on the other hand, had 6 buttons. It included the concept of a 'RUN' button.. added to the other buttons would give 6 a side. Control Panel pictures attached to illustrate. I did notice one of the control panel pictures for MK II was actually a MK III panel (for mk2r14 to be precise), which had a MK II label on the face of the panel, but clearly shows MK III on the top of the panel in multiple places.
No.04786 hap Developer Aug 8, 2009, 21:10	note about button 6 in source code: /* Note-the real MK2 board has a special cable designed for SF2 cab conversions that has the 2 SF2 Medium punch/kick buttons as block buttons for MK2. The secondary block button registers in test mode, but does not have an indicator light show up. During gameplay, the second block only functions temporarily. You can hold the button, but the character will only take a block position for 1 second. This is correct behavior. */ ---- I assume this lockup would happen on a real mk2r14 board too if connected to a 6-button cab, rev 1.4 was not a wide release according to history.dat.
No.11356 Firewave Senior Tester Jan 4, 2015, 19:40	I cannot get MAME to crash. It also doesn't cause any problem to just map the button. The game just freezes when I press it in-game or freezes after leaving the switch test.
No.11357 Haze Senior Tester Jan 4, 2015, 22:30	yeah, we're generally a lot safer these days when CPUs end up in the weeds, at least on non-recompiler cores. chances are this is an original game bug, the code to support that button (which is optional) is broken, and simply causes the game to freeze / watchdog reset because it crashes the code.