.NET 11 runtime drops older CPUs

Microsoft is raising the minimum hardware baseline for the .NET 11 runtime. According to the report, newer instruction sets will now be mandatory on both x86/x64 and Arm64 architectures, meaning .NET 11 applications may not run on older processors and could display a message saying the current CPU is missing one or more baseline instruction sets.

Two main reasons drive the change. As the article notes, supporting very old hardware adds significant complexity to the codebase and creates a "lowest common denominator" that AOT targets must default to. The update also aims to align with the hardware requirements operating systems already document and enforce. On Windows, the Arm64 baseline now requires the LSE instruction set, which matches Windows 11 and the Arm64 chips officially supported by Windows 10.

Apple hardware requirements remain unchanged; the M1 chips are described as roughly equivalent to armv8.5-a. On Linux, devices that only support AdvSimd, such as the Raspberry Pi, are still supported. However, the ReadyToRun target now includes LSE, which may add startup JIT overhead on some supported hardware. On x86, the baseline moves to x86-64-v2, while the ReadyToRun target moves to x86-64-v3 for Windows and Linux.

Separately, .NET 11 introduces Runtime Async V2, a significant step toward replacing compiler-generated state machines with runtime-managed suspension and resumption. According to the report, this produces cleaner stack traces, better debuggability, and lower overhead. The feature is in preview and requires a specific project property to opt in.