This problem exists even among different CPUs that all implement the M extension in hardware -- or different CPUs in ISAs where multiply and divide are not opti

This problem exists even among different CPUs that all implement the M extension in hardware -- or different CPUs in ISAs where multiply and divide are not optional, such as x86 or aarch64. The worst (but conforming) hardware implementations are barely better than the best software emulations -- and maybe worse if the software emulation is running on a wide OoO CPU.