[vivekv]

I am neither a compiler writer or an OS guru. Just an old c programmer. In this article it looks like the entire CPU instruction set was designed to emulate pdp11 to ensure c compatibility. So my naive question. What is stopping a Microprocessor manufacturer to have two instruction sets one that is compatible and one that allows us to fully utilise the modern CPU but with a different programming paradigm? Is that too expensive or hard to do? I genuinely don't know.

[GTP]

I think that there's just isn't any commercial incentive, as we have a ton of legacy C code and the CPU will have to run anyway in the "legacy" mode to run your OS, be it Linux, Windows or MacOS.