Usually this comes coupled with a period-correct OS, i.e. HP-UX. Yes, you could do an image loader for HP-UX bins on another OS, but that level of technical co

Usually this comes coupled with a period-correct OS, i.e. HP-UX. Yes, you could do an image loader for HP-UX bins on another OS, but that level of technical competence is rare. The reason why OS people do ports - portable software is good software. Avoiding ISA monoculture avoids shortcuts in kernel architecture. Some ISAs (alpha, sparc64) easily trigger invalid assumptions on ordering, alignment, endianness, etc improving overall quality. Alternative archs are also a great way to learn about areas of the system that are "done", so you can go fix and improve the things that were assumed to be "done" once you have requisite background.