There may be some SDL switch (environment variable) to force output on a specific monitor.

Sadly there is no solution whatsoever for this problem the developers of Dosbox never intended their software to be used on a second display of any kind and most likely never will...

PunkMaister wrote:

Sadly there is no solution whatsoever for this problem the developers of Dosbox never intended their software to be used on a second display of any kind and most likely never will...

That is SDL's problem, not DosBox's

Try this:
http://dualmonitortool.sourceforge.net/swapscreen.html

Nifty little tool, works like a charm for me. Only thing to do is change the shortcut to something different than Ctrl+<F12>, else it'll interfere with DOSBox.

I have been running DOSBOX on a 37" LCDTV as a second monitor. I don't recall trying to use full screen, because if I set the window size to one of the 3x modes, it is quite large enough for the limited resolution of old DOS games. The 3x window keeps the old 4:3 screen ratio which is what I want also. I don't want to see old games stretched out to a widescreen ration

Riyune wrote:

The 3x window keeps the old 4:3 screen ratio which is what I want also. I don't want to see old games stretched out to a widescreen ration

You should be able to configure your graphics card to maintain the correct aspect ratio in fullscreen. Your TV might have an appropriate way to force the aspect ratio, too.

If you set fullresolution= to your screen's native pixel dimensions _and_ aspect=true, you shouldn't get any kind of stretching.

As for switching monitors, if you're using Windows 7, Win+P is a very handy keyboard shortcut.

I imagine simply adjusting the resolution of DOS box to the second monitors resolution, and simply dragging it over would work also. Tho im on Windows 11 for my main, others may be on 7 or 8

Alistar1776 wrote on 2022-05-16, 04:33:

I imagine simply adjusting the resolution of DOS box to the second monitors resolution, and simply dragging it over would work also. Tho im on Windows 11 for my main, others may be on 7 or 8

I don't think this allows for running dosbox in a secondary monitor fullscreen. The reason this would be desirable for many people is that they run an older VGA CRT monitor as a secondary in order to play the games in a more contemporaneous way. AFAIK, the problem is SDL needing to launch on the primary and because DosBox runs with SDL, you have to use a third party utility to achieve desired results. I believe third party tools basically just automate the switching of the system's primary monitor, which is the other work around. However, it's a real PITA to go in and switch your desktop to 640x480 and back on Windows 10/11, so a seamless solution would be amazing.

But it's been years since I looked into this, so maybe the problem has been solved.