GoKawiilOxide builds open-source sp-emu to emulate Cortex-M7/M33 chips in its rack simulator
Oxide has released sp-emu, an open-source tool that emulates Cortex-M7 and Cortex-M33 microcontrollers on illumos and Linux (x86 and ARM), replacing an earlier simulation-only stub called SpSim. The emulated devices run Oxide's Hubris firmware directly and communicate over sockets with the Management Gateway Service and Inter-Processor Communication Channel, allowing the company's Voxel virtual lab to interact with them as if they were real service processors. A key engineering challenge was replicating time: since Hubris schedules work off a 1ms SysTick and the emulator has no wall clock, the team built a custom clock that counts instructions rather than real time.
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Moving from happy-path simulation to true emulation lets Oxide test edge cases and failure modes in its embedded root-of-trust and service processor software without needing physical hardware for every scenario, which could speed up development and catch bugs earlier. Open-sourcing sp-emu suggests Oxide wants outside scrutiny or adoption of its emulation approach, potentially benefiting other projects using Hubris firmware or similar embedded architectures. The instruction-based clock design highlights a broader challenge in hardware emulation: reconciling the deterministic timing assumptions of embedded code with the variable speed of emulated execution.
- Oxide released sp-emu, an open-source emulator for Cortex-M7 and Cortex-M33 microcontrollers running on illumos and Linux.
- The tool replaces a simpler simulation stub (SpSim) to provide higher-fidelity testing beyond happy-path scenarios.
- Because the emulator lacks real wall-clock timing, Oxide engineered a custom clock based on counting instructions to replicate Hubris's 1ms SysTick scheduling.
Source: oxide.computer — Steve Karam, 2026-10-14
Published there as: “Virtual Oxide Labs: Emulating a Full Oxide Rack”
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