INT 21 U - DBLSPACE.BIN - IOCTL - FLUSH OR INVALIDATE INTERNAL CACHES           
	AX = 4405h
	BL = drive number (00h = default, 01h = A:, etc)
	CX = 000Ah (size of DSPACKET structure)
	DS:DX -> DSPACKET structure (see #01537)
Return: CF clear if IOCTL successful -- check DSPACKET for actual status
	    AX = number of bytes actually transferred
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
Note:	this call is identical to the documented AX=4404h
SeeAlso: AX=4404h"DBLSPACE",INT 2F/AX=4A11h/BX=0000h


Format of DoubleSpace DSPACKET structure:
Offset	Size	Description	(Table 01537)
 00h	WORD	signature 444Dh ("DM")
 02h	BYTE	command code
		46h ('F') flush internal caches
		49h ('I') flush and invalidate internal caches
 03h	WORD	result code
		(ret) 4F4Bh ("OK") if successful, else unchanged
 05h  5 BYTEs	padding