The ARM-based M series is a RISC design rather than Intel's x86 CISC architecture. RISC circuits use less complex instructions, run cooler and thus save battery, which is why an ARM chip is used ...

Having worked closely with the RISC-V International open-standards group, we’ve ensured that our RISC-V MCUs are poised to help customers win new sockets in consumer, medical, industrial, and IoT ...

For example, the IBM PowerPC (a RISC architecture) has an ISA of a similar size to the IBM System 370 (a CISC architecture). Meanwhile, the DEC PDP-8 (a CISC architecture) only has 8 instructions.