INT 21 U - OS/2 v2.1 Virtual DOS MachineA special type of virtual machine provided by OS/2 version 2.0, in which a copy of MS-DOS or an MS-DOS compatible operating system (or even an incompatible 8086 operating system) is run and appears to have full control of the system.  See also Virtual Machine, INT 21h Function 64h. - GET LASTDRIVE
	AH = 64h
	DX = 0003h (function number)
	CX = 636Ch (magic value, "cl")
	BX = 0000h (indicates special request)
Return: AL = highest drive supported
Notes:	if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
	  in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
	used by WinOS2
	not supported by OS/2 Warp 3.0, check list of lists instead (see #01627)
SeeAlso: AH=52h