DOSBox-X update fixes Xargon and adds an OS-free legal branch

The DOSBox-X project has released version 2026.03.29. The update brings new bug fixes to the emulator and introduces a separate OS-free branch to comply with emerging legal requirements. Both versions are available on the project's GitHub page.

DOSBox-X is a fork of the original DOSBox project. The original DOSBox focuses entirely on getting classic DOS games to run on modern systems with minimal configuration. DOSBox-X goes much further. It aims for complete and accurate hardware emulation. It supports Windows 3.x, Windows 9x, Windows ME, and even Japanese PC-98 hardware. I mainly use DOSBox-X for Sierra games and Win 3.x games, but its actual scope covers everything from demoscene productions to obscure MIDI setups. It also includes drop-down menus and a graphical interface to make tweaking settings easier than editing text files.

Stripping out MS-DOS

The most unusual part of this release is the creation of the main-osfree branch. Going forward, development will happen across two distinct versions. The standard master branch keeps the fully functional built-in MS-DOS emulation that users expect. The main-osfree branch disables that built-in OS completely. It can only boot a guest operating system provided by the user.

This split exists for users in jurisdictions that enforce OS-level age verification laws. The developers stated that main-osfree is "for use in jurisdictions that enforce or wish to enforce OS level age verification, and therefore, may consider the MS-DOS emulation an OS that is subject to those laws." Because the standard version of DOSBox-X includes its own emulated DOS environment out of the box, it could technically be classified as an operating system. The OS-free version sidesteps the issue entirely. Users in those regions can download the stripped-down version and install their own copy of DOS or Windows to stay compliant.

Xargon menus load faster now

On the emulation side, the update fixes a specific CPU Idle callback bug. The emulator now strictly limits this callback to processing IRQs and a single CPU instruction. Previously, system calls using the Idle callback could vary their delay times based on other emulator events.

This caused major headaches if you had "scanline render on demand" enabled. In the 1993 Epic MegaGames platformer Xargon, that specific setting caused the game to take five to ten times longer just to transition between the title screen and the main menu. Epic MegaGames released Xargon during the height of the DOS shareware era, and it relies on specific timing tricks that modern emulators sometimes struggle to replicate. The new CPU Idle limit solves the menu delay completely.

The update also patches a memory allocation error in California Games II. The 1990 Epyx sports sequel occasionally miscalculates and asks the system for an excessively large block of memory during a resize operation. When the request inevitably fails, DOSBox-X no longer sets ownership of the failed block to the program. This prevents the game from crashing and allows the half-pipe surfing to continue uninterrupted.

OS/2 support and VS2026 builds

Other updates focus on compatibility and cross-platform cleanup. The emulator now has OS/2 support for tinyfiledialogs, the built-in browser, and external programs. Mac users get a fix for garbled text messages that appeared when opening image files from the dropdown menu. The Mac build also corrects an XCOPY argument parsing error to handle switches appended directly to file paths.

Finally, the project has added experimental 64-bit Visual Studio 2026 nightly builds. The emulator has grown massive over the last decade, and having automated builds helps catch regressions before they break another obscure 1990s platformer.