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Weird bug in my emulator! [SOLVED]
http://forums.nesdev.com/viewtopic.php?f=3&t=15470
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Author:  Zepper [ Mon Jan 30, 2017 5:55 pm ]
Post subject:  Weird bug in my emulator! [SOLVED]

1. Running the Stars Demo (PD), I got an invalid opcode ($12), and the emulator tries to RESET.
2. Loading a new ROM makes the bug to trigger... see the screenshot. Not only that game, but any other.

WTF is that?

Attachments:
bug01.png
bug01.png [ 215.48 KiB | Viewed 1082 times ]
bug02.png
bug02.png [ 167.43 KiB | Viewed 1082 times ]

Author:  DementedPurple [ Mon Jan 30, 2017 6:35 pm ]
Post subject:  Re: Weird bug in my emulator!

It is some assembly code error. An opcode is a number for the instruction that is running. What ROM are you playing? I'd recommend using Nestopia as your emulator.

http://nestopia.sourceforge.net/

Author:  Zepper [ Mon Jan 30, 2017 7:07 pm ]
Post subject:  Re: Weird bug in my emulator!

DementedPurple wrote:
It is some assembly code error. An opcode is a number for the instruction that is running. What ROM are you playing? I'd recommend using Nestopia as your emulator.

http://nestopia.sourceforge.net/

You must be kidding...

Author:  Alyosha_TAS [ Mon Jan 30, 2017 7:34 pm ]
Post subject:  Re: Weird bug in my emulator!

Zepper wrote:
1. Running the Stars Demo (PD), I got an invalid opcode ($12), and the emulator tries to RESET.
2. Loading a new ROM makes the bug to trigger... see the screenshot. Not only that game, but any other.

WTF is that?


1. The ROM ends up reading from un-cleared RAM starting at $0784. Emulators that initilize RAM with $FF will end up eventually at instruciton $12. If you initialize all RAM to 0 instead, the demo should run just fine.

2. Not sure aside from stating the obvious that something isn't being reset properly.

Author:  Zepper [ Mon Jan 30, 2017 7:41 pm ]
Post subject:  Re: Weird bug in my emulator!

Alyosha_TAS wrote:
1. The ROM ends up reading from un-cleared RAM starting at $0784. Emulators that initilize RAM with $FF will end up eventually at instruciton $12. If you initialize all RAM to 0 instead, the demo should run just fine.

Yeah, that's a known problem. ^_^;;

Quote:
2. Not sure aside from stating the obvious that something isn't being reset properly.

Did you said... OBVIOUS? :lol:

Joke aside, it's not happening on soft/hard reset, or even when I load another ROM. Weird and found it by accident.

Author:  tepples [ Mon Jan 30, 2017 7:46 pm ]
Post subject:  Re: Weird bug in my emulator!

Added to list of bugs in widespread homebrew and hacks

Author:  Zepper [ Mon Jan 30, 2017 8:13 pm ]
Post subject:  Re: Weird bug in my emulator!

Found the problem. The gfx frame pointer wasn't being set to zero. Well, it was an obscure problem... but I guess details won't be interesting anyways. ^_^;;

Author:  Dwedit [ Thu Feb 02, 2017 11:32 am ]
Post subject:  Re: Weird bug in my emulator! [SOLVED]

What's going on with Chu Chu Rocket?

Author:  Zepper [ Thu Feb 02, 2017 1:26 pm ]
Post subject:  Re: Weird bug in my emulator! [SOLVED]

Dwedit wrote:
What's going on with Chu Chu Rocket?

Nothing. 8-) It was a bug in my emulator frame pointer.

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