Default speed settings

By default, DOSBox tries to figure out what the correct speed for your game or application is. Sometimes, your game runs too fast. Or it just runs too slow. You can see the speed set by DOSBox in the title bar of the application window. It most likely says CPU speed: 3000 cycles or CPU speed: max 100% cycles, depending on the application you've started. There are two ways of changing this speed for DOSBox. One is when the game is running, the other is through the DOSBox options file.

Changing the speed while DOSBox is running

When DOSBox is running, you can alter the speed with the following short keys:

  • Press CTRL and F11 to decrease the speed
  • Press CTRL and F12 to increase the speed

Please note that when the status bar says the speed is max 100% cycles, you cannot increase the speed. This means that all your computer's processing power is used if necessary. So if you need to increase speed, there's something seriously wrong with either your computer or the software you try to run.

Changing the speed permanently through the options file

To set an alternative default speed that always will be used when you start DOSBox, you need to edit the configuration file.

  • Open the DOSBox configuration file:
    • Windows 7: Press CTRL + ESC (or Start button), type in dosbox and the options file DOSBox 0.7x Options should appear in the search results, click it
    • Windows 8 and Windows 10: Press the Windows key + Q, type in dosbox, and the options file DOSBox 0.7x Options should appear in the search results, click it
  • Look for the [cpu] section
  • Set cycles=auto to cycles=max to make sure DOSBox can use all your computer's processing power if necessary.
  • Set cycles=auto to cycles=xxxx, where xxxx is the number of instructions each millisecond. Whether an application runs ok with a certain number is for you to find out.

Other useful DOSBox info

The DOSBox wiki is the place to be for information about the workings of this DOS emulator: