If `acpi_mps_check` returns `1` it means that we disable local [APIC](http://en.wikipedia.org/wiki/Advanced_Programmable_Interrupt_Controller) and clear `X86_FEATURE_APIC` bit in the of the current CPU with the `setup_clear_cpu_cap` macro. (more about CPU mask you can read in the...
Since we have loaded a new `Global Descriptor Table` and the CPU has transitioned to a new mode (`64-bit` mode in our case), we set up the segment registers again at the beginning of the `startup_64` function:```assembly .code64 ...