By the end of its operation in 1956, ENIAC contained 18,000 vacuum tubes; 7,200 crystal diodes; 1,500 relays; 70,000 resistors; 10,000 capacitors; and approximately 5,000,000 hand-soldered joints. It weighed more than , was roughly in size, occupied and consumed 150 kW of electricity. This power requirement led to the rumor that whenever the computer was switched on, lights in Philadelphia dimmed. Input was possible from an IBM card reader and an IBM card punch was used for output. These cards could be used to produce printed output offline using an IBM accounting machine, such as the IBM 405. While ENIAC had no system to store memory in its inception, these punch cards could be used for external memory storage. In 1953, a 100-word magnetic-core memory built by the Burroughs Corporation was added to ENIAC.