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Associate III
August 14, 2026
Question

STM32CubeIDE STM32F303K8 offers an unexpected mtune

  • August 14, 2026
  • 0 replies
  • 5 views

When building in STM32CubeIDE 2.1.1, and targeting an STM32F303K8,

  • Project properties
  • C/C++ Build
  • Settings
  • MCU GCC Compiler
  • Miscellaneous
  • Near the bottom, observe a checkbox for -mtune=cortex-a35.

This option really does have effect in the gcc command line, and that really does significantly alter the compiled machine code.

But… why is this allowed in the UI? Why would this tuning option appear specifically for the A35, when the STM32F303K8 is an M4? By default, the makefile does correctly add -mcpu=cortex-m4.