Simple and stable aren't the most important part: AFAIK anybody can implement a CPU or an emulator with RISC-V ISA, which isn't the case for the other ISA.. The

Simple and stable aren't the most important part: AFAIK anybody can implement a CPU or an emulator with RISC-V ISA, which isn't the case for the other ISA.. There are a few exception such as OpenPower but you can't really buy CPU with those ISA.