+.PP
+If more than 4 disk drives are configured in the system,
+.I iostat
+displays only the first 4 drives, with priority given
+to Massbus disk drives (i.e. if both Unibus and Massbus
+drives are present and the total number of drives exceeds
+4, then some number of Unibus drives will not be displayed
+in favor of the Massbus drives). To force
+.I iostat
+to display specific drives, their names may be supplied on
+the command line.