Interrupt 67h	Expanded Memory Specification
Function  4Eh	Page Map Functions
SubFunc   02h	Swap Page Map
entry	AH	4Eh
	AL	02h
	DS:SI	Pointer to page map array
return  AH      status (see Int\67f\40)
		00h	Function Successful
		ES:DI	Pointer to Previous Page Map Array
note 1) Array is a 1024-byte area which will be filled with two words for each
	handle being used (first word is handle number, second is number of
	pages associated with it)