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Ms. Pac Man blue maze bug fix
#364399 - 03/19/17 06:00 AM
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Some guy fixed the blue maze bug in Ms. Pac Man by changing a single byte of code, check out http://donhodges.com/ms_pacman_bugs.htm
Anyway, I was wondering how I could access the code of the Ms. Pac Man rom so I could do this fix myself. Google didn't really help me here. Thanks for any help
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364400 - 03/19/17 06:06 AM
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They won't officially implement that code to fix it. Unless it's added as a cheat. That glitch is accurate to the arcade. I know because I played Ms. Pac-Man at my local Golf N Stuff for years and would occasionally run into it
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| Moose |
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364402 - 03/19/17 09:50 AM
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> Some guy fixed the blue maze bug in Ms. Pac Man by changing a single byte of code,
> check out http://donhodges.com/ms_pacman_bugs.htm
Hey, that's not "some guy", Don has done a lot of great work over many years tracking down the causes of strange bugs and behaviour in games. 
> Anyway, I was wondering how I could access the code of the Ms. Pac Man rom so I could
> do this fix myself. Google didn't really help me here. Thanks for any help
If you have done a little computer programming, then it is pretty easy. Don gives you the memory locations and the before and after byte values. If I get some time later today, I'll create more detailed instructions.
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| Moose |
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Re: Ms. Pac Man blue maze bug fix
[Re: Moose]
#364403 - 03/19/17 10:42 AM
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OK, had a chance to do some hunting around. Here are some instructions to help you generate the fixed roms if you want to:
Download HxD (freeware, http://mh-nexus.de/hxd/) and unzip it to a folder and double click on the HxD.exe.
Unzip your Ms Pacman roms and drag and drop pacman.6e onto HxD.
Fixing the Blue Maze Bug
In HxD, press Ctrl-G (go to) and enter 058B and click OK, and then type 41 to replace 4A.
Ms. Pac Man's Marquee Bug and Fix
The mem location for this one 3F7D, is beyond the range of any of the files in my old Ms Pacman rom set. Sorry, cannot help with this one.
Another obscure bug
In HxD, press Ctrl-G (go to) and enter 0C1D and click OK, and then type 00 to replace 15.
Follow my instructions above and you will fix 2 of the 3 bugs / errors.
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Moose
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Re: Ms. Pac Man blue maze bug fix
[Re: Moose]
#364427 - 03/19/17 07:28 PM
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Thanks but MAME won't accept the rom after the modification to fix the blue maze bug. I didn't think MAME would care about 1 byte changing but oh well, thanks anyway
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| casm |
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Cinematronics > *
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364450 - 03/20/17 01:27 AM
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> Thanks but MAME won't accept the rom after the modification to fix the blue maze bug.
> I didn't think MAME would care about 1 byte changing but oh well, thanks anyway
This thread may be of some help to you.
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364460 - 03/20/17 08:12 AM
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> I didn't think MAME would care about 1 byte changing but oh well, thanks anyway
What sort of derailed train of thought would lead to you thinking that?
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Re: Ms. Pac Man blue maze bug fix
[Re: MooglyGuy]
#364472 - 03/20/17 02:47 PM
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What? It's 1 byte, why wouldn't I think that?
Edited by saturatedfats (03/20/17 02:49 PM)
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364474 - 03/20/17 03:09 PM
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> What? It's 1 byte, why wouldn't I think that?
You wouldn't think that an emulator, which openly states that its intention is the accurate preservation of digital (and, to an extent, analog) data, would care about a byte being changed?
Were you under the impression that the team keeps track of individual files' CRC32 and SHA1 hashes just for fun?
Code:
ROM_LOAD( "5e.cpu", 0x0000, 0x1000, CRC(18442c37) SHA1(fac445d15731532364315852492b48470039c0ca) )
When you mistype a password, does it baffle you as to why it doesn't work, because hey, "it's just one byte"? Really?
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364476 - 03/20/17 03:19 PM
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Well, when I posted that the MAME devs wouldn't change it, that mighta been a good clue to you that you wouldn't be able to just do it yourself
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Re: Ms. Pac Man blue maze bug fix
[Re: MooglyGuy]
#364477 - 03/20/17 03:23 PM
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> > What? It's 1 byte, why wouldn't I think that?
>
> You wouldn't think that an emulator, which openly states that its intention is the
> accurate preservation of digital (and, to an extent, analog) data, would care about a
> byte being changed?
>
> Were you under the impression that the team keeps track of individual files' CRC32
> and SHA1 hashes just for fun?
>
> ROM_LOAD( "5e.cpu", 0x0000, 0x1000, CRC(18442c37)
> SHA1(fac445d15731532364315852492b48470039c0ca) )
>
>
> When you mistype a password, does it baffle you as to why it doesn't work, because
> hey, "it's just one byte"? Really?
Funny thing is MAME won't actually care, at least if you run it from the command line, it will tell you that the ROM is incorrect then attempt to run it anyway. It's not going to pass an audit or show as available in an unofficial UI build that way because it's not the expected file but there's no actual barrier in MAME to prevent it from running.
Of course it would make more sense to do it with the cheat engine, as a cheat than hacking the files, I thought somebody already had actually.
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Re: Ms. Pac Man blue maze bug fix
[Re: MooglyGuy]
#364478 - 03/20/17 03:27 PM
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I just wanted to emulate my personal favorite arcade game without some bugs, sorry that my lack of knowledge about MAME offends people here
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364487 - 03/20/17 06:16 PM
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If you want to faithfully emulate your fave game, then it comes with the bugs that were in the original arcade. The blue screen is very infrequent & really shouldn't bother you that much. The only time I see it is when I try to insert a coin & play the game before the 1st ghost appears in the attract mode. Just wait for Blinky to show up, then you should have no probs. Or you can insert coin & press start VERY fast and the blue maze glitch shouldn't occur.
Edited by Envisaged0ne (03/20/17 06:17 PM)
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Re: Ms. Pac Man blue maze bug fix
[Re: Envisaged0ne]
#364488 - 03/20/17 06:44 PM
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Well, I guess you're right, it doesn't matter that much at all
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364489 - 03/20/17 07:05 PM
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> Well, I guess you're right, it doesn't matter that much at all
There is someone who has applied all patches listed on that Don Hodges page, as far as I can tell, into one modified romset: mspacmap - Ms. Pacman (patched) and it is available to play in emulator HBMAME located here.
While it doesn't show you how it is done if you want to do it yourself, the issues are corrected and if you obtain the rom (or figure it out yourself), you can play it there as the hashes will match.
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Re: Ms. Pac Man blue maze bug fix
[Re: Tafoid]
#364494 - 03/20/17 07:43 PM
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Wow, thanks, that actually worked
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| Stiletto |
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Re: Ms. Pac Man blue maze bug fix
[Re: Moose]
#364505 - 03/20/17 10:09 PM
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364511 - 03/21/17 04:56 AM
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| R. Belmont |
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Re: Ms. Pac Man blue maze bug fix
[Re: saturatedfats]
#364605 - 03/24/17 08:15 PM
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> Thanks but MAME won't accept the rom after the modification to fix the blue maze bug.
> I didn't think MAME would care about 1 byte changing but oh well, thanks anyway
One byte being wrong can be the difference between a fully playable game and a black screen. MAME verifies ROMs as much as is humanly possible, because guaranteeing you have the same ROMs the original MAMEdev did is the only way MAME can guarantee you will get the same outcome.
Does this make sense?
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