Finally transitioned into 64-bit mode, so the actual OS can start getting written now. Not going to explain every step in detail since it’s always the same , but simple: built page tables using 2MB pages so the fourth paging level (the 4KB page table) could be skipped entirely, set up the stack, and did the rest of the long-mode setup (PAE, the EFER long-mode-enable bit, then paging itself) before the far jump into 64-bit code.