Felix86 26.09 update makes x86 emulation on RISC-V chips 30% faster

The open source felix86 project says its September release is 30% quicker than August's, closes gaps with native performance, and adds Steam game profiles and a HUD.

AI-drafted from 2 sources. This story was written with AI from the outside reporting listed under Sources, and checked by automated tools before it went up. The originals have the full detail.

Felix86, the open source emulator that lets x86-64 Linux and Windows software run on RISC-V hardware, has shipped its September update. According to the release notes, version 26.09 is roughly 30% faster than the previous release, alongside accuracy fixes, new per-game Steam profiles, and a HUD overlay.

Felix86 is a userspace emulator: it translates x86-64 instructions into RISC-V ones on the fly so software built for Intel and AMD chips can run on the growing crop of RISC-V boards and, eventually, laptops. That matters because RISC-V is an open instruction set architecture with no licence fees attached, and its hardware ecosystem is still short of native software. Projects like felix86, along with the more established QEMU, are the bridge until enough of that software gets ported directly.

Why the benchmarks are the story

The developers tested felix86 26.08 against 26.09 and against native performance on a SpacemiT K3 board, a RISC-V single board computer, running a set of standard benchmarks including 7-Zip, Coremark, Dhrystone, OpenSSL, SQLite, Stockfish, x264 and zstd. The gains are uneven but real: 7-Zip decompression improved by 60.7% month on month, x264 encoding by 44%, while Dhrystone barely moved at 2.1%. Taken together, the team calculates a geometric mean improvement of 30%, which is the headline figure in the release title. Some benchmarks now reach past 80% of native RISC-V speed, up from around a quarter to a half the previous month.

The more striking comparison is against QEMU 10.2.1, the widely used general purpose emulator that many RISC-V projects fall back on. With TSO emulation enabled on both, felix86 comes out well ahead across the board, and QEMU is reported to have crashed outright on the x264 test. TSO, or total store order, is a memory ordering guarantee that x86 chips provide by default and that RISC-V does not; emulating it correctly is one of the trickier and slower parts of running x86 code on RISC-V, and the developers note that only the multi-threaded Stockfish benchmark forced it on for this comparison, hence the bigger relative drop there.

Steam profiles and a HUD, but light on detail

Beyond raw speed, the release title also flags Steam game profiles and HUD integration, though the published notes seen so far focus mostly on the benchmark methodology and toolchain used to build them. The accompanying screenshots on the felix86 site show recognisable Steam titles apparently running under the emulator, including what looks like the horse racing sim Uma Musume Pretty Derby and an isometric anime combat game, suggesting the profiles are aimed at smoothing over per-game quirks rather than being a general fix. Exactly what the profiles configure, and how the HUD is meant to be used, is not spelled out in the material available, so treat that part as a feature to watch rather than one fully explained yet.

What is still unclear

The benchmark numbers come from the felix86 developers themselves, run on their own hardware with hand tuned build flags, so independent verification will matter, particularly since the r/emulation discussion thread is where much of the early scrutiny is likely to land. It is also worth remembering that these are synthetic workloads rather than full game sessions, so the real world experience of running a Steam library through felix86 on a K3 board may look different again. For anyone tracking RISC-V as a viable desktop platform, though, a credible open source path from x86 binaries to that hardware, one that is now measurably closing the gap on QEMU and on native performance, is the more durable part of this story.

Sources

Image: felix86.com