According to [1] in the section on initializing from reset, Intel CPUs boot to one of three modes: * Read mode has 1MB of memory and is 16 bit. * Flat protect

According to [1] in the section on initializing from reset, Intel CPUs boot to one of three modes: * Read mode has 1MB of memory and is 16 bit. * Flat protected mode which is 32 bit and takes interrupts * Segmented Protected mode which is 64 bit (w/ 32 bit emulation) and is used by operating systems to protect memory In this tutorial, your boot mode depends on what GRUB boots you in. [1] http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/minimal-intel-architecture-boot-loader-paper.pdf http://www.intel.com/content/dam/www/public/us/en/documents/...