Int 21 Fn 4405  U - Dblspace.bin - Ioctl - Flush Or Invalidate Internal C  [k]

   AX = 4405h
   BL = drive number (00h = default, 01h = A:, etc)
   CX = 000Ah (size of DSPACKET structure)
   DS:DX -> DSPACKET structure (see #1224)

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 #1366 at AH=59h/BX=0000h)

Note:  this call is identical to the documented AX=4404h

See Also: AX=4404h"DBLSPACE",INT 2F/AX=4A11h/BX=0000h

Format of DoubleSpace DSPACKET structure:
Offset Size    Description (Table 1224)
 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