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They haven't gone with a 64Bit ARM core. The ARMv8*M* isn't 64bit unlike ARMv8R and ARMv8A (the nomenclature can get confusing). The differences between ARMv7M
by crest 2y ago
They haven't gone with a 64Bit ARM core. The ARMv8*M* isn't 64bit unlike ARMv8R and ARMv8A (the nomenclature can get confusing). The differences between ARMv7M (especially with the optional DSP and FPU extension) and ARMv8M mainline are fairly minor unless you go bigger with an M55 or M85 which (optionally) adds the Helium SIMD extension. At he low end ARMv8M baseline adds a few quality of life features over ARMv6M (e.g. the ability to reasonably efficiently load large immediate values without resorting to constant pool). Also the MPU got cleaned up to make it a little less annoying to configure.
- rwmj 2y agoThanks for the clarification. Confusing terminology!
- pm215 2y agoARMv8A and ARMv8R can both be pure 32 bit as well, incidentally -- e.g. Cortex-A32 and Cortex-R52. v8A added 64 bit, but it didn't take away 32 bit. It's not until v9A that 32 bit at the OS level was removed, and even there it's still allowed to implement 32 bit support for userspace.