AH = 89h BH = IRQ8 interrupt vector offset BL = IRQ0 interrupt vector offset CX = offset into protected mode CS to jump ES:SI = pointer to Global Descriptor Table (GDT) on return: CF = 0 if successful = 1 if error - switches 286 and 386 machines into protected mode to take advantage of advanced feature and extended memory - Global descriptor table must be setup before interrupt - normal BIOS functions are not available after the switch