It wasn&#x27;t just x86, it was the fact that IBM released the entire documentation for the PC architecture up to the AT, including the BIOS source code (which was copyrighted, so competitors could not just copy it, but they could certainly study its function and produce a different but compatible implementation.)<p>For the PC, things started taking a turn for the worse with EFI and SecureBoot, but before that it was quite open.