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Question on "ignore illegal instructions" config
https://www.emaculation.com/forum/viewtopic.php?f=20&t=8425
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Author:  toshiba1 [ Sat Sep 13, 2014 7:42 pm ]
Post subject:  Question on "ignore illegal instructions" config

Looks like the Windows 'SheepShaverGUI.exe' does not allow you to affect the 'Ignore Illegal Instructions' config in the prefs file (which is the item 'ignoreillegal').

"Ignore illegal memory accesses" ignoresegv <true|false>
"Ignore illegal instructions" ignoreillegal <true|false>

Seems it defaults to 'false'. Is this the recommended setting?

Thanks

toshiba1

Author:  Ronald P. Regensburg [ Sun Sep 14, 2014 11:04 am ]
Post subject:  Re: Question on "ignore illegal instructions" config

Discussing the settings in the Memory/Misc tab, the SheepShaver for Windows setup manual recommends enabling "Ignore Illegal Memory Accesses":
Quote:
Note 2 : Although not shown in the figure below, it is best to also tick “Ignore Illegal Memory Accesses”.

"Ignore illegal instructions" can indeed not be set in the Windows GUI. As far as I am aware, it should best be left at its default value.

Author:  toshiba1 [ Mon Sep 15, 2014 12:30 am ]
Post subject:  Re: Question on "ignore illegal instructions" config

interesting. These posts below claim that the 'ignore illegal instructions' set to TRUE improved stability in some programs.

viewtopic.php?f=20&t=5754&p=30520&hilit=ignoreillegal#p30520

viewtopic.php?f=20&t=8262&p=47129&hilit=Ignore+Illegal+Instructions#p47129

viewtopic.php?f=20&t=7656&p=43496&hilit=Ignore+Illegal+Instructions#p43496

Also found a typo in this post, Cat_7 was supposed to refer to 'ignoresegv' for "Ignore illegal memory accesses", not 'ignoreillegal' (which I'm sure is a common mistake):

viewtopic.php?f=20&t=7111&hilit=ignoreillegal

toshiba1

Author:  emendelson [ Mon Sep 15, 2014 2:19 am ]
Post subject:  Re: Question on "ignore illegal instructions" config

You are asking about the Windows version. The posts you reference are about the OS X version.

Author:  toshiba1 [ Mon Sep 15, 2014 2:28 am ]
Post subject:  Re: Question on "ignore illegal instructions" config

Can you explain why that would make a difference? I admit, I'm not an expert in emulation, any info you have would help :)

toshiba1

Author:  emendelson [ Mon Sep 15, 2014 2:50 am ]
Post subject:  Re: Question on "ignore illegal instructions" config

If I knew, I would be glad to explain. But the two versions work very differently, and I'm not sure anyone now knows exactly why.

Author:  Ronald P. Regensburg [ Mon Sep 15, 2014 8:23 am ]
Post subject:  Re: Question on "ignore illegal instructions" config

The original developers left the project years ago and now only few people (if any) have insight in all of the BasiliskII/SheepShaver code. Most changes in the past years were for the OSX version only.

Enabling "Ignore Illegal Instructions" is normally not recommended also in the OSX version, but it can be tried to see if it can prevent problems with programs that ask for instructions that are not available in these emulators. In many cases those programs will not run properly anyway, regardless this setting.

Is there a special reason why you ask about this setting? You can change "ignoreillegal false" to "ignoreillegal true" yourself in the prefs file using a proper text editor (Notepad will do) and see if that makes any difference in your setup.

Author:  toshiba1 [ Mon Sep 15, 2014 12:36 pm ]
Post subject:  Re: Question on "ignore illegal instructions" config

I asked the question originally because I was looking to improve stability overall. I had crashes/hangs fairly often.

So as of late, I set both ignoresegv and ignoreillegal to true.

The results seem to be good thus far. Running 06-05-2013 build in Windows x64. I'm going to continue to pound on it like this and see what happens =)

Author:  sentient06 [ Mon Oct 20, 2014 12:52 pm ]
Post subject:  Re: Question on "ignore illegal instructions" config

In my tests on OSX, I realised SheepShaver may respond better/worse depending on the combination of ROM file and system. For example, I always use "Mac OS ROM 1.4" with Mac OS 8.6. I am guessing it is because this rom was taken from an 8.6 system. If I try using other versions like 1.6 (from Mac OS ROM update), chances are it will crash much more often. I am not sure why it happens, maybe some ROM calls are simply different depending on the system and ROM.

So try combining other ROMs with your system, maybe it becomes more stable.

I am not sure about Old World ROMs, though, I always stick to Power Mac 7500 versions 1 or 2.

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