Beyond

A forum for anything about the Steem Engine STE emulator, comments, problems, bug reports etc. Steven Seagal regularly provides updated versions of the original STEem code. The current version is v3.9.4.

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keops
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Beyond

Postby keops » Fri May 06, 2005 10:10 pm

It would be really cool to have Beyond demo by Kruz running with Steem :)

http://no-fragments.atari.org/no_fragments_01/MSA/K/KRUZ/BEYOND.MSA

This demo kicked ass when it was released

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leglod
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Postby leglod » Sat May 07, 2005 2:32 pm

Hi...
Not run for me whit Steem , Tos 1.62 1 mo 8 mhz standard ???
Grilichili bruit de crayon sur papier.
Les dinosaures de la micro :) ... Mini-Z ...

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Postby Steem Authors » Thu May 12, 2005 11:18 am

This is a protection problem, they are very difficult to debug unfortunately. It would probably be easier for someone to crack it than for us to emulate it.

Russ

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keops
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Postby keops » Thu May 12, 2005 6:22 pm

Yeah I know, my message implied that anyone willing to patch it would be most welcome ;)

Leonard? :)

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Postby jarskukkeli » Thu May 12, 2005 6:58 pm

If I remember correct Beyond worked some time ago with Steem version 1.x or 2.x or something like that...

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keili
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Postby keili » Thu May 19, 2005 8:13 am

Haven't tested it myself, but i have been told, that it worked with Steem ver. 2, TOS 1.0, 1MB.
BTW, same with Aladin, the MAC emu, worked with Steem 2.06, but not 3.x.

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Postby ijor » Thu May 19, 2005 4:07 pm

I tried some debugging. It seems to be a tough case, but it's quite interesting.

The program has some anti-hacking techniques that seems to be handled correctly by Steem. Prefetch tricks, address exception, I don't see anything Steem makes wrong there.

Then there is an illegal exception. I don't know for sure if that's intentional or not. On one hand the program doesn't install an illegal exception handler, so you might think it wasn't intentionally provoked. But on the other hand, the program installs some code to be run at reset time. So is possible that it intentionally wants the machine to (warm) reset.

When TOS handles the illegal exception, it is just about to reset the machine. Before doing that it makes a Gemdos call that provokes a Bus Error. Again, I don't know if this exception is intentional or not. Might be the problem is here and Gemdos should not bomb at this point.

But the problem might be something else. Is possible that all of this is intentinal and it happens in a real machine. And after the second bombing the machine makes a warm reset, and the program continues.

This doesn't happen in Steem. It seems that Steem detects the "two bombs in a row" and forces a hard crash and a cold reset. Perhaps this "hard crash" detection changed between 2.X and 3.X.

Or perhaps is something completely different. Hard to be sure without fruther investigation.

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Postby Steem Authors » Sun May 22, 2005 11:12 am

I think we have some problems with emulating when the ST warm resets itself, we don't really know what triggers it. Crash and burns should only occur when an exception happens and sp is invalid, that would always cause a halt on a real ST as far as we know.

The change that stopped Aladin working was correct emulation of bus errors in low memory, writes to address 0 to 8, I don't know if that could have something to do with it. But protection routines are just so difficult to work out, it is very possible it only worked in old versions due to a Steem bug.

Russ

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Re: Beyond

Postby Steven Seagal » Sun Feb 05, 2012 10:05 pm

I raise this topic for the usual brags and also for documentation purposes, after all I stumbled on it earlier while trying to fix the problem, and it's full of false tracks, and the fix is a CPU emulation improvement.
The problem happens at the first exception on the instruction

Code: Select all

1716 MOVE.W (A0)+,(A1)+


where A1 contains $11 (odd -> crash)
On a real ST, A1 will never be incremented after the exception, so it keeps $11 and that value is later used for code decoding in another memory zone. In Steem, A1 was incremented even before the exception triggered and the program would later crash & burn. I find it strange that it worked in Steem 2.
Of course it's fixed in the kick-ass build!
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Steem SSE: http://sourceforge.net/projects/steemsse


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