Int 2F Fn 4A11  - Dblspace.bin - "getextrainfo" - Determine Number Of Dis  [k]

   AX = 4A11h
   BX = 0009h
   DL = compressed drive number (0=A:)

Return: AX = status (see also #2490)
       0000h successful
       CL = number of DISK_UNIT structures allocated
             (see AX=4A11h/BX=0005h)
       CH = DoubleGuard enabled-checks bitflags in bits 6-0 (DOS 6.2)

Note:  the DoubleGuard checks are enabled or disabled as a block by the
     DoubleGuard= line in DBLSPACE.INI; they may be individually set with
     the CheckSum= line.

See Also: AX=4A11h/BX=0000h,AX=4A11h/BX=0008h