IBM drum storage

In addition to the drums used as main memory by IBM, e.g., IBM 305, IBM 650, IBM 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 2048 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 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 3490 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 and 1301 DASD. One or two 7631 controllers can attach to a computer system, but the system can still attach only a total of five DASD. When used with a 709x, a track holds 2796 six-bit characters, and a 7320 unit holds 1,118,400 characters. Data transfer rate is 202,800 characters per second.[6]

The 7320 attaches to a System/360 through a channel and an 2841 Storage Control unit. Each 2841 can attach up to eight 7320 devices. When used with System/360, a track holds 2081 eight-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The 7320 was superseded by the IBM 2301 in mid-1966.[8][9]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 3500 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. Average access time is 8.6 msec, and the data transfer rate is 1.2 million 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 312.5 thousand 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

References
  1. Principles Of Operation Type 701 and Associated Equipment (PDF). IBM Corporation. 1953. Retrieved May 22, 2021.
  2. Type 702 Preliminary Manual Of Instruction (PDF). IBM Corporation. 1954. Retrieved May 22, 2021.
  3. IBM 704 electronic data-processing machine (PDF). IBM Corporation. 1955. Retrieved May 22, 2021.
  4. 705 Data Processing System Reference Manual (PDF). 1959. Retrieved May 22, 2021.
  5. IBM Corporation. "DPD chronology". IBM Archives. Retrieved Dec 6, 2019.
  6. IBM 7320 Drum Storage (PDF). 1962. {{cite book}}: |work= ignored (help)
  7. "IBM 7320 Drum Storage" (PDF). 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 (PDF). p. 41. A26-5988-0. 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. {{cite book}}: |work= ignored (help)
  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.
  9. Office of Naval Research (October 1964). "IBM System 360". Digital Computer Newsletter. Office of Naval Research - Mathematical Sciences Division. 16 (4): 7–8. Retrieved Dec 6, 2019.
  10. "IBM 2301 Drum Storage" (PDF). IBM System/360 Component Descriptions -- 2820 Storage Control and 2301 Drum Storage (PDF). September 1968. pp. 30–31. A22-6895-2. Retrieved April 18, 2021. {{cite book}}: |work= ignored (help)
  11. "IBM 2303 Drum Storage" (PDF). IBM System/360 Component Descriptions - 2841 and Associated DASD (PDF). December 1969. pp. 74–76. GA26-5988-7. 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. {{cite book}}: |work= ignored (help)
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