If you continue that thought experiment, you'd very quickly run into the issue that the way the 386 interfaces memory is hopelessly primitive and not a good mat

If you continue that thought experiment, you'd very quickly run into the issue that the way the 386 interfaces memory is hopelessly primitive and not a good match for running 1000s of cores in parallel. A large reason why out of order speculative execution is needed for performance is to deal with the memory latencies that appear in such a system.