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Screen tearing issue

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First post, by rex0

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Pretty much every game that I tried, such as Batman Forever(sidecroller) and MK Trilogy, they all have very noticeable screen tearing. Is there any way to fix it?

Reply 1 of 14, by Peter Swinkels

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I have tried many games and other stuff in DOSBox and never seen screen tearing. What kind of computer are you using? Also, it would help if you provided your version of DOSBox and the contents of your DOSBox configuration file.

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Reply 2 of 14, by rex0

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I'd prefer you try the games that I mentioned above. I have a core i5 (3rd gen). 60hz monitor. Using Dosbox 0.74-3. Config attached below.

Reply 3 of 14, by Peter Swinkels

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I don’t have those games so I can’t try them. And what does MK stand for?

EDIT:
In the case of your Batman game, did you mean this one: https://www.myabandonware.com/game/batman-forever-2ez ? If so, it would be relatively late and therefore relatively advanced game for MS-DOS, perhaps DOSBox's emulation for late 90's games hasn't been perfected yet? (EDIT 2: According to the compatibility page the game should work fine though.) Anyway your computer's specs seem to be more than enough. Judging from your DOBox.conf file you might want to make the following changes:

core=simple
cputype=pentium_slow
cycles=7500

That would make DOSBox emulate a Pentium 75MHz which would have been typical for around 1996.

EDIT 3:
According to the game's manual : https://d1.myabandonware.com/f/mkp/Batman-For … nual_DOS_EN.pdf you need a 80486 33Mhz. It might well be your DOSBox is running way too fast with cycles=auto.

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Reply 4 of 14, by rex0

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MK = Mortal Kombat

Yes, that Batman Forever game is the correct one. I tried the changes for core, cputype and cycles that you have suggested, but they make the game run super slow.

Reply 5 of 14, by jmarsh

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The short version is you need a monitor with a higher refresh rate.

DOSBox disables vsync in order to be able to output 70Hz (the typical refresh rate used for most resolutions under DOS). If it didn't there would be lag when using a 60HZ screen.

Reply 6 of 14, by rex0

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Really? That's pretty weird. Never thought I'd require a monitor over 60hz for old Dos games. Even the most modern games don't need that.

Btw I saw a Vsync option in Dosbox Staging config, but enabling it doesn't seem to have any effect. How come?

Reply 7 of 14, by Peter Swinkels

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@rex0:
That is really odd, what I recommended was more than twice what the manual I linked to stated.

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Reply 8 of 14, by feda

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Peter Swinkels wrote on 2023-12-16, 22:18:

@rex0:
That is really odd, what I recommended was more than twice what the manual I linked to stated.

That's because you're wrong. Dosbox cycles aren't directly equivalent to processor speed in mhz.
7500 cycles does not equal 75 mhz. For 75 mhz you need closer to 50 000 cycles.
As for tearing, I don't think it's possible to fix in Dosbox. I've had that problem in a bunch of games myself.

Reply 9 of 14, by Peter Swinkels

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@feda, okay so I am mistaken, but how did you calculate 50000 cycles equals 75 mhz?

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Reply 10 of 14, by feda

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This is an approximation based on benchmarks. Dosbox-X claims that Pentium 75 mhz is ~43500 cycles.
Also check out the table at the bottom of this page: https://www.dosbox.com/wiki/Performance
But like I said, it's just an approximation and benchmark tests might not be accurate either.
There is no exact equivalence Re: Cycles and Mhz

Reply 11 of 14, by dr.zeissler

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Is there really a dosgame that scrolls like butter in dosbox like it is on the real machine?

Last edited by dr.zeissler on 2023-12-17, 13:05. Edited 1 time in total.

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Reply 12 of 14, by jmarsh

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Sure, if you're playing a game that runs in 640x480 or higher (60Hz) or use a monitor that can do 70Hz (and have the OS configured to use that refresh rate).

Reply 13 of 14, by Kalle

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Is there really a dosgame that scrolls like butter in dosbox like it is on the real machine?

The 60/70Hz issue applies to a real machine as well. Sure, there were no issues with CRTs, also my old LCD monitor Philips Brilliance 150P supports 70Hz and scrolls smoothly in DOS.
But both my 20" LCD monitors Philips Brillance 200P and NEC MultiSync LCD2070NX have issues, as the Philips runs at a fixed rate of 60Hz and the NEC at 59,3Hz (which also causes additional stutter every second).
When hooking up those monitors to a DOS machine and displaying a 70Hz side scroller, the Philips stutters (as it can't display 70Hz, it has to convert it to 60), but there is no tearing. The NEC stutters and shows tearing.

As you see, even on a real machine 70Hz games can be problematic depending on the monitor. As already said, games that ran at 60Hz shouldn't be a problem.

Reply 14 of 14, by dr.zeissler

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The older TFT's do works in 70hz. It's not dosgames alone... jazz2 requires 70hz for smooth scrolling!

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