IBM 2501
The IBM 2501 is a punched-card reader from IBM with models for the System/360 and System/370 mainframe systems and for the IBM System/360 Model 20, the IBM 1130 and IBM System/3 minicomputers. 2501 models can read 80-column cards at either 600 or 1000 cards per minute (CPM).[1]
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| Type | Punch card reader |
|---|---|
| Release date | 1965 |
| Predecessor | IBM 1402 |
| Related | IBM 2540 |
The 2501 is no longer sold, but is simulated in software on current IBM systems.[2]
Models
The 2501 comes in four models depending on speed and attachment features. Models for mainframe use come with an integrated control unit that performs the functions of a control unit required by other devices.
The A1 and A2 are for the IBM 1130.[3]
| Model | speed (CPM) | Integrated control unit? |
|---|---|---|
| A1 | 600 | no |
| A2 | 1000 | no |
| B1 | 600 | yes |
| B2 | 1000 | yes |
Usage
The 2501 uses a photoelectric sensor to read the data punched in the card. Cards are read serially (column by column) and the reader uses a simplified "straight through" card path. "Each column is read twice and the two readings are compared to check reading accuracy."[4]
In a mainframe environment the 2501 was frequently used for mainframe input in an "open shop" environment where users submitted their own jobs.[5][6]
On an 1130 system the 2501 can be used in addition to the IBM 1442. Since the 1442 has a maximum speed of 300 or 400 CPM attaching a 2501 provides a significant increase in read speed and lower CPU usage.
The System/3 normally processes 96-column punched card; the 2501 provides alternative input for shops that require the ability to read 80-column cards.
Features
A special feature (RPQ) is available for all models to allow them to read optically marked (OMR) cards.[7]
References
- IBM Corporation (1967). IBM Field Engineering Theory of Operation: 2501 Card Reader Model A (PDF). Retrieved March 12, 2021.
- IBM Corporation. "Identifying I/O device requirements". IBM Knowledge Center. Retrieved July 29, 2016.
- IBM 1130 Functional Characteristics (PDF) (seventh ed.). IBM. April 1972. p. 3. GA26-5881-6.
- Shubs, Howard. "Punched Card Input/Output Devices". IBM1130.net. Retrieved July 29, 2016.
- Da Cruz, Frank. "The IBM 2501 Card Reader". Columbia University Computing History. Columbia University. Retrieved July 29, 2016.
- University of Michigan (September 1980). Introduction to the Computing Center. p. 93. Retrieved July 29, 2016.
- IBM Corporation (November 1969). IBM 1130 Computing System, IBM System/360 Models 25, 30, 40, 44, 50, 65, and IBM System/360 Model 20-Special Feature Description Optical Mark Reading for IBM 2501 Card Reader and IBM 2560 Multi-Function Card Machine (PDF). Retrieved March 12, 2021.