INT 16 - PC-Cache v6+ - FLUSH CACHE AND DISABLE DELAYED WRITES
        AX = FFA5h
        CX = CCCCh
Return: AX = ??? (apparently either 0000h or sectors_in_cache - 5)
Note:   delayed writes are automatically disabled on EXECing
          (see INT 21/AH=4Bh) a program named either WIN.CO? or DV.E??;
          however, delayed writes are not automatically reenabled upon the
          program's termination in v6.
SeeAlso: AX=FFA5h/CX=FFFFh