Overview

At its core, DOSBox Staging emulates a PC: a CPU running at a configurable speed, memory laid out the way DOS software expects, and a DOS environment sitting on top of both. CPU, Memory, and DOS cover those three pieces. Machine types covers PCjr and Tandy as complete machines, and Localisation covers language, country, and keyboard settings.

The rest of this page covers general emulator behaviour that doesn’t belong anywhere else: window focus, the screensaver, and disk speed. Most of this is just about how DOSBox Staging behaves as an application on your desktop, but disk speed emulation is the exception.

General behaviour

When you switch away from DOSBox Staging (e.g., by pressing Alt+Tab), the emulator keeps running in the background by default, sound and all. If you’d rather not hear game music while you’re doing something else, mute_when_inactive silences the audio output whenever the window loses focus. pause_when_inactive goes a step further and pauses the entire emulation, which is useful for games that don’t have a built-in pause function.

The screensaver setting controls whether the OS screensaver is allowed to activate while DOSBox Staging is running. By default, it’s blocked to prevent the screensaver from kicking in during a long cutscene or a game that doesn’t require constant input.

Disk speed

By default, DOSBox Staging reads and writes floppy and hard disk data almost instantly. That’s fine for most games, and actually advantageous when installing games that copy large files to the C: drive, but a couple of situations call for slowing it down to match real period hardware:

• PCjr booter games. Many early PCjr titles boot directly off floppy disk rather than from DOS, and some of these were timed against the PCjr’s real (slow) floppy drive. Setting floppy_disk_speed to a period-correct value can help these run and load the way they were designed to.

• Games that measure disk I/O speed at startup. A handful of titles — Deus, Ishar 3, Robinson’s Requiem, Time Warriors, and the 1993 CD-ROM version of Dragon’s Lair — run a “speed check” on disk I/O at startup and refuse to run if it looks too fast, since DOSBox Staging’s default disk I/O is unrealistically fast compared to period hardware. Setting hard_disk_speed = fast fixes the check and, as a side effect, lets you run these games with much higher CPU cycles settings (100,000–150,000 range).

• Authenticity. If you want the experience of period-correct floppy swapping and load times rather than a modern instant-load feel. Throttled disk speed also pairs naturally with disk noise — the two settings work in tandem, since the clicking and spinning sounds only feel authentic when access isn’t instantaneous.

These are edge cases — leave floppy_disk_speed and hard_disk_speed at maximum unless a specific game needs otherwise.

Configuration settings

Window & focus behaviour

You can set these in the [sdl] configuration sections.

mute_when_inactive

Mute the sound when the window is inactive.

Possible values: on, off default

pause_when_inactive

Pause emulation when the window is inactive.

Possible values: on, off default

screensaver

Use allow or block to override the SDL_VIDEO_ALLOW_SCREENSAVER environment variable which usually blocks the OS screensaver while the emulator is running.

Possible values: auto default, allow, block

Disk speed

You can set these in the [dosbox] configuration sections.

floppy_disk_speed

Set the emulated floppy disk speed.

Possible values:

• maximum default – As fast as possible, no slowdown.
• fast – Extra-high density (ED) floppy speed (~120 kB/s).
• medium – High density (HD) floppy speed (~60 kB/s).
• slow – Double density (DD) floppy speed (~30 kB/s).

hard_disk_speed

Set the emulated hard disk speed.

Possible values:

• maximum default – As fast as possible, no slowdown.
• fast – Typical mid-1990s hard disk speed (~15 MB/s).
• medium – Typical early 1990s hard disk speed (~2.5 MB/s).
• slow – Typical 1980s hard disk speed (~600 kB/s).