1953: diode plug-in unit and the IBM 650
IBM 650
The IBM 650 had a magnetic drum memory, which served as secure programs and data. This consisted of a 35cm-long, cobalt- nickel- coated drum with a diameter of 10cm. The magnetic drum rotated at a speed of 200 revolutions per second and was scanned from 100- 200 read- write- heads.
Compared to standard hard disk
- 1 read- write head
- 10cm long
- 90- 120 revolutions per second
On his relatively cheap, large storage up to 2000 words had room. Through a special address format could a new command be loaded while another was completed. By dint of an internal applied error detection, the IBM was classified as fast and reliable – perfect condition in order to establish itself in the growing market.
