Function 89h    Switch Processor to Protected Mode            (AT, XT/286, PS/2) 
entry   AH      89h 
	BH      interrupt number of IRQ 8 (IRQ 9Fh use next 7 interrupts) 
	BL      interrupt number of IRQ 0 (IRQ 17h use next 7 interrupts) 
	CX      offset into protected mode CS to jump to 
	DS:SI   pointer to Global Descriptor Table for protected mode 
		offset  00h     null descriptor 
			08h     GDT descriptor 
			10h     IDT descriptor 
			18h     DS 
			20h     ES 
			28h     SS 
			30h     CS 
			38h     uninitialized, used to build descriptor for 
			        BIOS CS 
return  AH      0FFh  error enabling address line 20 
	CF      set on error