IBM drum storage

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Short description: Data-storage devices

In early computers drum storage consisted of a large metal cylinder, coated on the outside surface with a ferromagnetic recording material. Drums were later largely replaced by the hard disk drive.

Drums were used as main memory by IBM in computers including the IBM 305 and IBM 650; IBM also offered drum devices as secondary storage for the 700/7000 series and System/360 series of computers.

IBM 731

The IBM 731 is a discontinued storage unit used on the IBM 701.[1] It has a storage capacity of 2,048 36-bit words (9,216 8-bit bytes).

IBM 732

The IBM 732 is a discontinued storage unit used on the IBM 702.[2] It has a storage capacity of 60,000 6-bit characters (45,000 8-bit bytes).

IBM 733

The IBM 733 is a discontinued storage unit used on the IBM 704[3] and IBM 709. It has a storage capacity of 8192 36-bit words (36,864 8-bit bytes).

IBM 734

The IBM 734 is a discontinued storage unit used on the IBM 705[4] It has a storage capacity of 60,000 6-bit characters (45,000 8-bit bytes).

IBM 7320

The IBM 7320 is a discontinued storage unit manufactured by IBM which was announced on December 10, 1962[5] for the IBM 7090 and 7094 computer systems, was retained for the earliest System/360 systems as a count key data device, and was discontinued in 1965. The 7320 is a vertically mounted head-per-track device with 449 tracks, 400 data tracks, 40 alternate tracks, and 9 clock/format tracks. The rotational speed is 3,490 rpm, so the average rotational delay is 8.6 milliseconds.[6]

Attachment to a 709x system is through an IBM 7909 Data Channel and an IBM 7631 File Control unit, which can attach up to five random-access storage units: a mix of 7320, 1301, and 1302 DASD. One or two 7631 controllers can attach to a computer system, but the system can still attach only a total of five DASD.[6] When used with a 709x, a track holds 2,796 6-bit characters, and a 7320 unit holds 1,118,400 characters.[lower-alpha 1] Data transfer rate is 202,800 characters per second.[6]

The 7320 attaches to a System/360 computer through a channel and an IBM 2841 Storage Control unit. Each 2841 can attach up to eight 7320 devices. When used with System/360, a track holds 2,081 8-bit bytes, and a 7320 unit holds 878,000 bytes. Data transfer rate is 135,000 bytes per second.[7]

The 7320 was superseded by the IBM 2301 in mid-1966.[8][9]

IBM 2301

The IBM 2301 is a magnetic drum storage device introduced in the late 1960s to "provide large capacity, direct access storage for IBM System/360 Models 65, 67, 75, or 85." The vertically mounted drum rotates at around 3,500 revolutions per minute, and has a head-per-track access mechanism and a capacity of 4 MB. The 2301 has 800 physical tracks; four physical tracks make up one logical track which is read or written as a unit. The 200 logical tracks have 20,483 bytes each. The average access time is 8.6 ms, and the data transfer rate is 1,200,000 bytes per second. The 2301 attaches to a System/360 via a selector channel and an IBM 2820 Storage Control Unit, which can control up to four 2301 units.[10]

IBM 2303

The IBM 2303 is a magnetic drum storage device with the same physical specifications as the IBM 2301. The difference is that the 2303 reads and writes one physical track at a time, rather than the four in the 2301, reducing the data transfer rate to 312,500 bytes per second. The 2303 attaches to System/360 through a channel and an IBM 2841 Storage Control Unit, which can attach up to two 2303 units.[11]

See also

Notes

  1. ↑ The actual capacity depends on the contents of the format track, but with full track formatting it is 2,796 6-bit characters/track and 1,118,400 characters/unit.

References

  1. ↑ Principles Of Operation Type 701 and Associated Equipment. IBM Corporation. 1953. http://www.bitsavers.org/pdf/ibm/701/24-6042-1_701_PrincOps.pdf. Retrieved May 22, 2021. 
  2. ↑ Type 702 Preliminary Manual Of Instruction. IBM Corporation. 1954. http://www.bitsavers.org/pdf/ibm/702/22-6173-1_702prelim_Feb56.pdf. Retrieved May 22, 2021. 
  3. ↑ IBM 704 electronic data-processing machine. IBM Corporation. 1955. http://www.bitsavers.org/pdf/ibm/704/24-6661-2_704_Manual_1955.pdf. Retrieved May 22, 2021. 
  4. ↑ 705 Data Processing System Reference Manual. 1959. http://www.bitsavers.org/pdf/ibm/705/A22-6506-0_705_Reference_Man_May59.pdf. Retrieved May 22, 2021. 
  5. ↑ IBM Corporation. "DPD chronology". https://www.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology2.html. 
  6. ↑ 6.0 6.1 6.2 IBM 7320 Drum Storage. 7090/7094 Data Processing Systems. IBM Corporation. 1962. http://bitsavers.org/pdf/ibm/7090/G22-6717_7320_7631_1962.pdf. 
  7. ↑ "IBM 7320 Drum Storage". 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. Systems Reference Library (First ed.). IBM. p. 41. A26-5988-0. http://bitsavers.org/pdf/ibm/2841/A26-5988-0_2841_2311_2321_7320_Descr.pdf. Retrieved Dec 6, 2019. "The drum is divided into 400 data tracks; each track has a read/write head and may contain up to 2,081 bytes of data. The maximum data transfer rate is 135 thousand bytes per second." 
  8. ↑ Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1991). IBM's 360 and Early 370 Systems. MIT Press. p. 272. ISBN 0-262-16123-0. https://archive.org/details/ibms360early370s0000pugh. 
  9. ↑ Office of Naval Research (October 1964). "IBM System 360". Digital Computer Newsletter (Office of Naval Research - Mathematical Sciences Division) 16 (4): 7–8. https://books.google.com/books?id=DR8pjs4SVR4C&pg=RA7-PA8. Retrieved Dec 6, 2019. 
  10. ↑ IBM System/360 Component Descriptions -- 2820 Storage Control and 2301 Drum Storage. Systems Reference Library (Third ed.). IBM Corporation. September 1968. pp. 30–31. A22-6895-2. http://bitsavers.org/pdf/ibm/2820/A22-6895-2_2820_2301_Component_Descr_Sep69.pdf. Retrieved April 18, 2021. 
  11. ↑ IBM System/360 Component Descriptions - 2841 and Associated DASD. Systems Reference Library (Eighth ed.). IBM Corporation. December 1969. pp. 74–76. GA26-5988-7. http://bitsavers.org/pdf/ibm/2841/GA26-5988-7_2841_DASD_Component_Descr_Dec69.pdf. Retrieved April 17, 2021. "Storage capacity: 3.913 million bytes. High speed accessibility: Rotational Delay Only: average 8.6ms. Fast data transfer to the processor: 303,800 bytes per second." 



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