Ok, I see. The S3’s "MMU" is just an external-memory mapper, not a virtual-memory MMU. The S31 apparently has both, that mapper plus an architectural CPU-side Sv32 MMU; that offers indeed a lot of interesting possibilities. Even sel4 would run on this machine as it seems. The ARM world has no microcontroller with a true MMU as far as I know. Risc-V now has at least two (here is the other one: https://www.bunniestudios.com/blog/2026/baochip-1x-a-mostly-...).