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Re: Experimental VGA patch

Posted on 2010-10-20, 09:37

What exactly do you mean with "delayed frame rate change"? I had a small application that could show tearing by redrawing the screen in adjustable intervals. If timing would have been precise the tearing "line" would have been adjustable and could have been "pushed out of the screen" in to the …

Re: Experimental VGA patch

Posted on 2010-10-20, 08:29

I've done a lot of capturing and tinkering with DOSBox and have disassembled a number of DOS demos. I think that the problem with SVGA demos is not that VSYNC isn't working, but that a lot of them actually time the VBLANK and then synchronize themselves to that time they have measured. They don't …

Re: VSYNC in DosBox (Mac OSX & OpenGL)

Posted on 2009-01-25, 22:34

Good to hear that the vsync-problem is nagging other people too. ;) If the game didn't tear on real hardware, it shouldn't tear on Dosbox This is not entirely true. I depends on the type of syncing the game/demo did. I encountered some that measured vsync timing and then relied on that. The problem …

Re: Demo application crashing.

Posted on 2008-02-11, 14:18

I unpacked the application and patched the EMMS instruction to 2 NOPs. Still, the patched EXE is crashing, and its not the EMMS instruction it is crashing at... It is still the same crash address and still a 06-Exception, there are no suspicious opcodes though. I'm a bit puzzled here.

Re: Demo application crashing.

Posted on 2008-02-06, 23:24

It crashes the ykhwong 0.72 CVS build. It does NOT crash the offcial 0.72. I'll report that to ykhwong's site. This was more about help to run that program than the instruction crashing DOSBox... Thanks for helping out guys. I decompressed the EXE and will now fire up IDA to fix this baby to make it …

Re: Demo application crashing.

Posted on 2008-02-06, 09:23

The unpacker is pmwunlit Found it, thanks. Well if you manage to compile the dosbox sources, you can simply add the emms to behave like a nop. I probably need some experimental stuff from the ykhwong build (vsync, ...). But if you point me to the file/function I need to patch I'll try to do it …

Re: Demo application crashing.

Posted on 2008-02-06, 08:49

pmwunpack Is this the packer? I couldn't find any supicious strings in the EXE. Google gives me absolutely nothing... I guess it is something internally used in the demogroup probably... Can you build dosbox from sources? Not atm. Did it with 0.65 once, so I guess I could. Do you suggest adding a …

Re: Demo application crashing.

Posted on 2008-02-06, 08:32

A dos game executing mmx stuff while not checking for the processor type is a common "problem"? DOSBox fully takes care of that in throwing exception6 which is what a real non-mmx processor does. I just didn't think DOSBox would crash because of that. But that's maybe just in the ytkwong build. I'm …

Re: Demo application crashing.

Posted on 2008-02-05, 18:27

Try Bochs Does it have a video capture capability?! I couldn't find information about that... I could use it to check out what opcode it executes though... The demo, if it uses MMX, fails to check the CPU type. Not good. People did nasty stuff in the past, but MMX wasn't that common back then, so I …

Re: Demo application crashing.

Posted on 2008-02-05, 18:19

I have a debugger build of Yk$%&whateverwongs experimental 0.72 builds. Can you point me to decent documentation about the debugger or tell me how to break program execution or step through the code? That it crashes DOSBox should be considered a bug though! Executing a bad program shouldn't crash it …

Re: Demo application crashing.

Posted on 2008-02-05, 18:07

A 80386 with MMX? Happy 🤣. I should write before I think... Nope, but i didn't check this demo yet, could be they're executing rubbish, too. I don't really know, because I don't know of a way to show the code being executed before the application crahes...

Demo application crashing.

Posted on 2008-02-05, 00:00

Hi people. I have an old DOS protected mode multimedia-presentation here I wanted to run ( http://www.scene.org/file.php?file=/parties/1998/assembly98/pcdemo/tour_by_.zip ). It always crashes at the same point however. I fired up a debug console, which prints this before dying and killing DOSBox …

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