Question on "ignore illegal instructions" config

About SheepShaver, a PPC Mac emulator for Windows, MacOS X, and Linux that can run System 7.5.3 to MacOS 9.0.4.

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toshiba1
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Question on "ignore illegal instructions" config

Post by toshiba1 »

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
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Ronald P. Regensburg
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Re: Question on "ignore illegal instructions" config

Post by Ronald P. Regensburg »

Discussing the settings in the Memory/Misc tab, the SheepShaver for Windows setup manual recommends enabling "Ignore Illegal Memory Accesses":
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.
toshiba1
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Re: Question on "ignore illegal instructions" config

Post by toshiba1 »

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

http://www.emaculation.com/forum/viewto ... gal#p30520

http://www.emaculation.com/forum/viewto ... ons#p47129

http://www.emaculation.com/forum/viewto ... ons#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):

http://www.emaculation.com/forum/viewto ... oreillegal

toshiba1
emendelson
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Re: Question on "ignore illegal instructions" config

Post by emendelson »

You are asking about the Windows version. The posts you reference are about the OS X version.
toshiba1
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Re: Question on "ignore illegal instructions" config

Post by toshiba1 »

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
emendelson
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Re: Question on "ignore illegal instructions" config

Post by emendelson »

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.
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Ronald P. Regensburg
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Re: Question on "ignore illegal instructions" config

Post by Ronald P. Regensburg »

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.
toshiba1
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Re: Question on "ignore illegal instructions" config

Post by toshiba1 »

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 =)
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sentient06
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Re: Question on "ignore illegal instructions" config

Post by sentient06 »

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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