Would you believe that you can take a relatively-modern Intel or AMD computer and install regular old MS-DOS on it? Well, you can (depending somewhat on the machine). Doing so will utterly waste the potential of such a system, but all of the legacy support structures are still in place to make such a thing feasible. Those legacy features are

Source: Hot Hardware – Intel’s X86S Proposal Cuts Legacy Cruft For Streamlined 64-Bit Only CPUs