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]
The 2501 is no longer sold, but is supported by software of current IBM systems.[2]
Models
The 2501 comes in four models depending of 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 cards, 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]
See also
- Punched card input/output
- Computer programming in the punched card era
References
- ↑ IBM Corporation (1967). IBM Field Engineering Theory of Operation: 2501 Card Reader Model A. http://bitsavers.trailing-edge.com/pdf/ibm/25xx/Y31-0069_2501_Card_Reader_FETOM_Feb67.pdf. Retrieved July 29, 2016.
- ↑ IBM Corporation. "Identifying I/O device requirements". https://www.ibm.com/support/knowledgecenter/SSLTBW_1.13.0/com.ibm.zos.r13.e0zb100/devsupt.htm. Retrieved July 29, 2016.
- ↑ IBM 1130 Functional Characteristics manual, p. 3
- ↑ Shubs, Howard. "Punched Card Input/Output Devices". http://www.ibm1130.net/functional/Cards.html. Retrieved July 29, 2016.
- ↑ Da Cruz, Frank. "The IBM 2501 Card Reader". Columbia University. http://www.columbia.edu/cu/computinghistory/2501.html. Retrieved July 29, 2016.
- ↑ University of Michigan (September 1980). Introduction to the Computing Center. p. 93. https://books.google.com/books?id=qJ0mP7wJ8xYC. 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. http://bitsavers.trailing-edge.com/pdf/ibm/25xx/GA15-8002-0_2501_2560_Mark_Sense_RPQ_Nov69.pdf. Retrieved July 29, 2016.
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