NEON is guaranteed to exist on everything, and this means you're never going to see Aarch64 replace the Cortex M0 and M3. That's fragmentation right there. Sev

NEON is guaranteed to exist on everything, and this means you're never going to see Aarch64 replace the Cortex M0 and M3. That's fragmentation right there. Severe fragmentation. Two completely incompatible ISAs. Small 32 bit RISC-V comes in smaller and lower power than An M0, and small 64 bit RISC-V is not much bigger than an M0 and is rather popular controlling something in the corner of a larger 64 bit SoC.