IBM 1405 DISK STORAGE SYSTEM

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The IBM 1405 Disk Storage Unit was announced in 1961 and was designed for use with the IBM 1400 series, medium scale business computers. The 1405 used improved technology to double the tracks per inch and bits per inch of track -- to achieve a fourfold increase in capacity -- compared to the IBM RAMAC 350 disk unit of 1956. The 1405 Model 1 had a storage capacity of 10 MB of data on twenty-five 24 inch disks, while the Model 2 had a storage capacity of 20 MB on fifty disks. In both models the disks are stacked vertically on a shaft rotating at 1200 rpm. When used with an IBM 1410 Data Processing System, up to five of the 1405s could be connected, for a max data total of 100 MB. In addition, a single 1405 of either model could be attached to an IBM 1401 Data Processing System. The 1405 Storage Unit remained in service until it was withdrawn in June of 1970.This model represents the fifty disk Model 2.