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PostPosted: Sun Jun 10, 2018 8:04 am 
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Space Cadet

Joined: Sun Jun 10, 2018 7:44 am
Posts: 5
Hi,

I'm trying to run Vampire Castle v7.0 with Mini vMac 3.5.8 and System 6.0.8. However, the game bombs out with an illegal instruction while drawing the intro screen.

Image

Image

Download here:
http://macintoshgarden.org/sites/macint ... Castle.sit
or here:
http://users.abo.fi/kilundqv/vampirecastle800k.dsk

The game supposedly works on real hardware, but I'm not able to verify that myself.

I've tried tinkering with MacsBug, but neither the Step commands nor breakpoints work as I'd expect them to, so I have no clue what's causing the game to bomb out.

Has anyone managed to get this game to run on an emulator? How should one go about troubleshooting this situation?


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PostPosted: Sun Jun 10, 2018 8:10 am 
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Location: Amsterdam, Netherlands
According to Macintosh Garden:
Quote:
This game appears to be incompatible with all current emulators, but it runs on a Mac Plus with System 6.0.8.

See: http://macintoshgarden.org/games/vampire-castle


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PostPosted: Sun Jun 10, 2018 8:21 am 
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Space Cadet

Joined: Sun Jun 10, 2018 7:44 am
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Hmm, yes. Those findings from approx. 2012-2014 are apparently still valid. However, noone claims to have done any more serious technical troubleshooting, so I guess that's what I'm hoping might happen now at some point. :smile: My experiments with MacsBug unfortunately didn't tell me anything. I'd like to find out what exactly is causing the game to crash and then see if something could be done about it. :smile:


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PostPosted: Sun Jun 10, 2018 10:39 am 
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Location: Germany
Maybe MiniVMac II is the one for trouble shooting?
The game at least starts with 6.0.7 but hangs due to an error immediately.

Image

After pressing a key, the game closes again - no surprise.

I am inclined to agree that no common emulator will run this game - including Qemu, Fusion PC and PCE. :(
I did not exactly try PCE MacPlus with 6.0.8.

The old VMac for DOS luckily runs Vampire Castle!
Rather slow with the 6800 VMac, maybe the 68020 will do better.
This is from Virtual Box running a DOS instance with VMac.

Image

A little work to set up, as DOS can´t use VBox extensions, so a helper VM to handle the files is needed too.
I could share my VBox VMs, but as you may have guessed, the greater parts are in German.

The VMac link fanman93 gave me almost ten years ago is still valid:
http://www.leb.net/vmac/download/DOS/vM ... OS-Bin.zip


Last edited by 24bit on Sun Jun 10, 2018 6:00 pm, edited 2 times in total.


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PostPosted: Sun Jun 10, 2018 5:52 pm 
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Space Cadet

Joined: Sun Jun 10, 2018 7:44 am
Posts: 5
Many thanks for trying all those different emulators, etc! :smile:

I did something funny just now, and suddenly I actually do get a proper intro screen for this game. :shock: The problem is, however, that I don't really have a logical explanation for what I did, i.e. to patch my .dsk file like this:
Code:
E:\mac>fc /B vampirecastle800k.dsk vampirecastle800kTEST.dsk
Comparing files vampirecastle800k.dsk and VAMPIRECASTLE800KTEST.DSK
0002EE71: D0 75

The result:
Image

The game engine is responding to commands, but I haven't yet tried to actually play.

Would anybody more technically knowledgeable than I like to explain why my little trick did what it did? :smile:


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PostPosted: Sun Jun 10, 2018 6:03 pm 
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Great you got things rolling!
Which MiniVMac build and OS did you use?
Please do consider sharing the working disk image at Macintoshgarden.
My DOS solution is rather a long shot. ;)


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PostPosted: Mon Jun 11, 2018 3:27 am 
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Looks like you changed an instruction -- I'm blanking on what the instruction would be, but likely you've NOP'd a CMP or JMP.


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PostPosted: Mon Jun 11, 2018 9:56 am 
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Space Cadet

Joined: Sun Jun 10, 2018 7:44 am
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Yes, what I was *trying* to do was to skip a JMP that I picked out sort of randomly. I'm surprised that it worked as well as it did, and I really can't give any sort of logical technical explanation for it. :P

I used Mini vMac 3.5.8 and System 6.0.8.

I just happened to notice that when the illegal instruction at 00f80000 occurred, the value of A0 was 00F80000. Thus, I started looking for 'JMP (A0)' instructions in RAM and found this:

Image

Then I looked for the hex data 4E D0 4E 75 00 00 00 CA in the disk image and took a shot in the dark and changed 4E D0 to 4E 75, i.e. JMP (A0) to RTS.

... but what was the purpose of all the code I might've skipped and why did the game crash in the emulator in the first place? :P

(I know a thing or two about 6502, but absolutely nothing about 68k).

Hey, user 24bit, that's great! You actually got the unpatched game running with vMac-0.1.9.5.DOS-Bin.zip .. !? :o Maybe I should try that as well, even if the game appears to be running very well with my method, too. However, I still haven't managed to kill the vampire. I'm not sure if that's just because I haven't yet thought of the right command or if it's due to my version of the game being broken somehow.


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PostPosted: Sat Jun 16, 2018 2:36 pm 
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Space Cadet

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All right, I managed to finish the game now, using my patched disk image and Mini vMac 3.5.8 with System 6.0.8. The entire time, it was rather obvious that the Axe would be an important part of the solution, but exactly how were you supposed to use it ... !? It only took me 30 years to find the answer to that question. :lol:


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PostPosted: Sat Jun 16, 2018 6:24 pm 
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Congrats for killing another un-dead. :)
If you find the time, you might try VMac in Windows or MacOS9.
Some kind people could dig out the executables. GNU/Linux and OS2 ports (and a few others) are still missing,
but the mainstream stuff has surfaced. http://macintoshgarden.org/apps/vmac-195
I still can´t use 6.0.8 with the stock app, but D-6.0.7 works for some reason I can´t tell.

MacTouch over at Macintoshgarden just pointed to the fact that the stock game runs fine with MinVMac II SSW 7.5.3.
No idea how I could miss trying that.

Image


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