This article describes the contents of the computer's physical memory at the moment that the BIOS jumps to your bootloader code. Real mode address space (< 1 MiB) When a typical x86 PC boots it will be in Real Mode, with an active BIOS. During the time the CPU remains in Real Mode, IRQ0 (the clock) will fire repeatedly, and the hardware that is used to boot the PC (floppy, hard disk, CD, Network c