Is this a thing today (or was it in the past)? Was Cyrix or Transmeta in such position? The Zilog Z80 is notoriously an extension over Intel 8080. I find it ha

Is this a thing today (or was it in the past)? Was Cyrix or Transmeta in such position? The Zilog Z80 is notoriously an extension over Intel 8080. I find it hard to believe and hard to enforce since emulators of various quality are practically everywhere (and not only for x86). QEMU?