Int 16 Fn FFA5  - PC-cache V6+ - Flush Cache And Disable Delayed Writes    [c]

   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.

See Also: AX=FFA5h/CX=AAAAh,AX=FFA5h/CX=FFFFh