TL;DR
Box64 v0.4.0 introduces multiple refactors, opcode and dynarec improvements, and broader platform support, including Steam on Loongarch, RISC-V and ARM64. Work continues on memory reclamation, synchronization support, and stability for experimental 32-bit compatibility.
What happened
Maintainer ptitSeb published Box64 v0.4.0 with a package of fixes, speedups, opcode implementations and refactors across the three supported backends: ARM64, RISC-V and Loongarch. The update adds a prefix opcode decoder to the interpreter and dynarec backends, reducing duplicated code and enabling automatic handling of many opcode variants. Steam’s Linux client is reported to run on ARM64, RISC-V and Loongarch builds (the Windows client also runs if preferred), while Box32 remains experimental and can still crash during downloads. Battle.net has become more stable and some games work, though success can vary by region and program version. The release also begins work on reclaiming memory from converted-but-unused native code blocks, with further improvements planned. The Loongarch backend saw notable progress but needs a 4K page-size kernel to run correctly. Capture and test footage for the release were produced using an Elgato HD60X and OBS on ARM64 machines.
Why it matters
- Broader platform support could expand native-like game compatibility on emerging CPU architectures such as Loongarch and RISC-V.
- The prefix opcode decoder and dynarec improvements reduce maintenance complexity and can improve emulation coverage without bespoke code.
- Memory-reclamation work may lower long-running memory usage for heavy apps such as Steam or applications using libcef variants.
- Advances in synchronization support (ESync/FSync/NTSync) affect multiplayer and launcher-heavy titles that rely on inter-process coordination.
Key facts
- Release: Box64 v0.4.0 announced on 3 January 2026 by ptitSeb.
- Supported platforms: ARM64, RISC-V and Loongarch backends received updates; Steam reported to run on all three (Linux client).
- Box32 (32-bit compatibility layer) remains experimental and unstable; improved but still prone to crashes when downloading via Steam.
- A new prefix opcode decoder was implemented in the interpreter and three dynarec backends, reducing duplicated source files.
- Initial mechanisms were added to identify converted native code blocks that appear unused so their memory can be freed; work is ongoing.
- Loongarch requires a 4K page-size kernel to run properly; distributions with 4K options include AOSC and a recently added Debian option.
- Capture and testing used an Elgato HD60X and OBS on ARM64 hardware; some ARM64 captures showed compression artifacts due to software encoding.
- ESync and FSync are supported but may cause synchronization issues with some launchers; NTSync shows promise but requires kernel and Wine/Proton-GE support.
- RISC-V dynarec reached a higher level of completion with contributions from PLCT Labs, though hardware address-space limits can affect DRM-heavy workloads.
What to watch next
- Further releases for continued memory-reclamation improvements and expanded dynarec loop optimizations.
- Ongoing testing and broader compatibility on RISC-V hardware; some features were still pending comprehensive testing at release.
- Wider adoption of NTSync support depending on kernel builds and bleeding-edge Wine/Proton-GE availability; not confirmed in the source if mainstream distros will enable it soon.
- Progress on Box32 stability and reduced crash frequency when downloading or using Steam features.
Quick glossary
- Box64: A userspace compatibility layer that runs x86_64 Linux binaries on non-x86_64 architectures by translating calls and recreating runtime behavior.
- Dynarec: Dynamic recompiler that converts blocks of guest architecture code into host-native code at runtime to improve performance.
- Loongarch: A processor architecture developed for certain RISC-based CPUs; used here as one of Box64’s supported backends.
- ESync / FSync / NTSync: Mechanisms used by Wine/Proton for inter-process synchronization. They aim to improve performance but have different kernel and compatibility requirements.
- Opcode prefix decoder: A component that interprets instruction prefix bytes to correctly handle less common or exotic instruction encodings without special-case hacks.
Reader FAQ
Does Box64 v0.4.0 run Steam on Loongarch?
Yes; the release notes report Steam running on Loongarch Linux, but it requires a 4K page-size kernel.
Is the Windows Steam client supported?
The post notes the Windows client also works if preferred, but the reported testing focused on the Linux client.
Is Box32 stable now?
No. Box32 remains experimental and unstable; stability has improved but crashes can still occur, for example during Steam downloads.
Can I use NTSync on common ARM64 distributions?
Not generally; Debian and Ubuntu on ARM64 still lacked NTSync in the kernels mentioned, while some distros like Armbian and AOSC on Loongarch had it enabled.
Categories BOX64 GAMING New Box64 v0.4.0 released Post author By ptitSeb Post date 3 January 2026 1 Comment on New Box64 v0.4.0 released Happy new year, and happy new release…
Sources
- Loongarch Improvements with Box64
- Box64 v0.4 Improves Support For DRM Protected Games …
- Box64 – Linux Userspace x86_64 Emulator with a twist …
- News – [Phoronix] Box64 v0.4 Improves Support For DRM …
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