Spent a lot of time watching the blinking lights on a DEC 11/34 while the 9-track ... s l o w l y ... advanced to ... Start ... loading the program. The boot switch had protective bars around it. Quite frequently the 9-track could not read the file start on the tape, indicated by rewinding and advancing over the same spot of tape. At which point you pushed the abort button, cleaned the tape read head, toggled the boot switch again ... and waited ...