Peripheral devices have always been much slower than core processing units. This was an especially severe problem for early mainframes. For example, a job which read punched cards or generated printed output directly was forced to run at the speed of the slow mechanical devices. The first spooling programs, such as IBM's "SPOOL System" (7070-IO-076) copied data from punched cards to magnetic tape, and from tape back to punched cards and printers. Hard disks, which are even faster and support random access, started to replace this use of magnetic tape in the middle 1960s, and by the 1970s had eliminated this use of tape.