Modes of Operation

Real-address mode

• Is the mode used on power-up or after a hard or soft reset.

• 16-bit registers.

• Segmented memory space (16 * segment + offset)

Protected mode

• Virtual memory, paging, multitasking, 32-bits, 64-bits.

Hypervisor mode

• Ring -1

System management mode

• "god" mode, ring -2

Management engine

• Ring -3.

Changing the mode of operation

• CLP (current protection level)

• system calls

• interrupts

• gates

  • call gates

  • trap gates

  • interrupt gates

  • task gates

• vmxon, vmxoff, vmlaunch, vmenter, vmexit, vmresume (virtual machine control structure).