If you are into retro-gaming you probably have some idea of what DOSBox is. If you're still not aware, it's the Disk Operating System (DOS) emulator. The project started several years ago, and it's aimed mostly towards video-games. It's quite mature and stable, and companies like GOG.com or Steam are using it, in most cases, to allow the execution of old games in modern computers. Have you ever tried to play a game pre-2000 in Windows 7, or even Windows XP? It usually won't run, as most of these games were written for DOS. Even when Windows 98 was already standardized, there was no reason to create a game that run on it natively. Even games that needed windows to run, still worked pretty much under DOS (it makes sense, as Windows itself was just, somehow, another layer over MS-DOS).


There are probably many more tweaks, but until now I didn't really need more. Also, notice that some particular games may be a bit picky, needing special settings for themselves.
Anyway, for this article, I'm taking for granted that you, fellow reader, know what DOSBox is, and just need to get somehow a better emulation for your old game. I must say I'm not an expert on DosBox, and most of my DOS knowledge has diluted during the past years. I wouldn't even know how to use the expanded memory anymore. Or, at least, I wouldn't recall the command.
Also, I'd like to point out that all these tips worked for me, but that doesn't mean they should work for your computer, and of course it doesn't mean it will work for every game. However, in my experience, most of these """""hacks""""" do work. Although if they break your computer, I take no responsibility.
Almost all the changes are done through DOSBox's configuration file. If you installed DOSBox yourself (I pity you) you'll find the configuration file under C:\Users\YOUR_USERNAME\AppData\Local\DOSBox in Windows Vista / Windows 7, and under %USERPROFILE%\Local Settings\Application Data\DOSBox\ in Windows XP. If I'm not mistaken, it will be in your home folder in Linux. The file is called dosbox-x.yz.conf, (x.yz being the version number of the software). Please, note that this file used to be called just dosbox.conf, and that's the name it'll have when downloading a game from GOG.com or Steam. By the way, in these particular cases, the configuration file will be somewhere on the game folder. Just search for *.conf, inside the root folder and something like dosbox*****.conf will appear. The name may vary depending on the game. Any text editor will be enough to modify the file.
Now, let's get started...

1) CPU Settings
There are two things we should be probably changing here, especially if we're trying to run a game we bought through a digital retailer, as they are usually leaving the default options which, well, are shit.
core=simple (default "auto")
The "auto" setting changes the way the core is emulated during runtime. It may mess up the game at some points. As an example, the first Gabriel Knight is impossible to get through with dynamic emulation. Still, dynamic emulation might give your game a great performance improvement. If that's the case, it's better to set it directly on the configuration file than letting DOSBox guess it by itself. Just mess around with the option and see what works better for you.
cycles=15000 (default "max")
In my experience, specific numbers work better. You might have to throttle them a bit until you find your "perfect" setting, although most games will run OK with a number between 15000 and 20000. Any processor nowadays can handle these values.
2) Video Settings
The video options of DOSBox are scattered through various different sections. There are a couple of important options under [sdl].
output=overlay (default "surface")
This setting is a bit tricky. You'll get the best image quality (as in the proper, crisp image) with surface. The overlay option should give you some extra performance, at the loss of almost no image quality, although it won't be that significant without the dynamic core parameter. Other options such as opengl or ddraw (Windows only) -could- give you some extra performance, but they depend a lot on your graphics card and its drivers. Apparently, NVIDIA cards work a bit better with opengl than the ATI counterparts. Still, again, any graphic card with less than two years should be able to handle these modes without any problem. It's also said that you'll get the worse image quality. Not in my experience. Also, keep in mind that some modes will work better in full screen, and some will benefit from windowed mode.
fulldouble=true (default "false")
This option should only be changed on some 3D games, where our FPS go far beyond infinity and flickering/tearing occurs. Most of the 2D games won't benefit from this option, so it may be better to leave it in "false".
Let's move to [render]:
aspect=true (default "false")
While most games won't benefit from this option, you might need it for some of them, especially if using non 4:3 screens (think of 3D games). It barely hits the performance of the emulation.
frameskip=0 (default "0")
If you can avoid using frameskip, do it. A value up to 2 is acceptable, but anything beyond that will be very noticeable, and probably reduce the quality of the experience more than it will improve it.
scaler=normal2x (default "normal2x")
This setting changes the way the games are scaled. Normal2x gives the best retro result, just using nearest neighbor scaling, thus showing bigger pixels at higher resolutions. If you want to get a "better" quality, as in using gradients and more rounded edges, I suggest hq2x or hq3x (remember we're multiplying pixels, so hq3x means you'll need a 1920x1440 resolution screen for a game originally displayed at 640x480).
Finally, let's check the [dosbox] options.
machine=svga_s3 (default "svga_s3")
Any other option should be only used for specific games, such as cga versions.
memsize=16 (default "16" or "8")
This option changes the amount of emulated video memory. Usually 16 is enough for any game, but you might want to check 24 or 32 for later games.
3) Other emulation options (sound, joystick, IPX...)
I've heard many times that it's a good idea to disable everything you're not using. I've never noticed more than (hardly) a 2% improvement in the best case scenario, disabling the joystick, non-used sound cards and network options. What do have an impact, however, are the rates on the soundcards, and the sbtype. Usually 44100 will sound better than 22050 in any game post-1995 (or any game that does have 44KHz sounds), and anything below this will probably sound like an old walkie-talkie. However, the lower the number, the better the performance.
Different Soundblaster emulation options will also bring different results. For example, you'll need sbpro2 to get stereo sound on some games.
4) More tweaks
When trying to play Theme Hospital some time ago, I stumbled upon DOS32A. This small "Advanced DOS Extender" is meant to replace DOS4GW.EXE, a file you will find in most DOS games. To use it, just create a backup of DOS4GW.EXE on your game folder and copy dos32a.exe to the same folder, renaming it to DOS4GW.EXE afterwards. Easy!
What does this program do? Basically just replacing the horrible default extender by a proper set of functions.
Taken from the official page of the project:
DOS/32 Advanced DOS Extender is a drop-in replacement for the popular DOS/4GW DOS Extender and compatibles. During 1990'es many software applications and games were developed using Watcom C/C++ and Fortran compilers which allowed DOS applications to run in 32-bit flat protected mode environment, e.g. be "DOS Extended." This functionality was provided by the DOS/4GW DOS Extender from Tenberry Software, a middleware product which at the time was bundled with Watcom tools. While being royalty-free, DOS/4GW was big, slow and lacked many important features, all in favour of its commercial (and rather expensive) siblings. To remedy the situation a number of independent projects set out to create a replacement of DOS/4GW that could match and exceed it in terms of features, performance and price. DOS/32A is the result of such a project.
There are probably many more tweaks, but until now I didn't really need more. Also, notice that some particular games may be a bit picky, needing special settings for themselves.
Do you know more tricks? Just post them!



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