IBM 2841

The IBM 2841 Storage Control Unit was a Direct Access Storage Device (DASD) control unit introduced with System/360 in 1964.

The 2841 was a microprogrammed control unit "intended for use in controlling access to a disk or strip file or a slow-speed drum storage unit." It attached to a standard System/360 channel,^[1] or could also be attached to an IBM 1130 or IBM 1800 Data Acquisition and Control System to add support for 2311 disks.

The 2841 was capable of attaching the following devices:

• IBM 1302 Disk Storage – up to four modules for a total of 448 mB. A special feature on the 2841 allowed attachment of an additional four modules.
• IBM 2311 Disk Storage Drive model 1 – up to eight disk drives for a total of 58 mB.
• IBM 2321 Data Cell – up to eight 2321s for a total of 3.2 gB.
• IBM 7320 Drum Storage – up to eight units for a total of 6.6 mB.

By December 1969 the IBM 7320 had been replaced by the much faster IBM 2303, which permitted up to two units for a total of 7.8 mB.

Besides the expansion feature for additional 1302s, the 2841 offered two-channel switch, scan, and record overflow special features.^[2]

DASD devices introduced after those mentioned did not use the 2841. For example the IBM 2314, the successor to the 2311, featured an integrated controller.^[3]

See also

• History of IBM magnetic disk drives
• Direct access storage device

Further Reading

• IBM System/360 Component Descriptions — 2841 Storage Control Unit, 2302 Disk Storage models 3 and 4, 2311 Disk Storage Drive, 2321 Data Cell Drive model 1, 7320 Drum Storage; first edition
• IBM System/360 Component Descriptions — 2841 and Associated DASD; eighth edition, December 1969 Adds the IBM 2303 and eliminates the IBM 7320
• IBM Field Engineering Theory of Operation—2841 Storage Control (Stage 2) describes the implementation details of the IBM 2841

References