In addition to the drums used as

main memory Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processin ...

by IBM in, e.g.,

IBM 305 The IBM 305 RAMAC was the first commercial computer that used a moving-head hard disk drive (magnetic disk storage) for secondary storage. The system was publicly announced on September 14, 1956,

IBM 650 The IBM 650 Magnetic Drum Data-Processing Machine is an early digital computer produced by IBM in the mid-1950s. It was the first mass-produced computer in the world. Almost 2,000 systems were produced, the last in 1962, and it was the firs ...

, IBM offered drum devices as

secondary storage Computer data storage or digital data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data. It is a core function and fundamental component of computers. The cent ...

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 The IBM 701 Electronic Data Processing Machine, known as the Defense Calculator while in development, was IBM’s first commercial scientific computer and its first series production mainframe computer, which was announced to the public on May 2 ...

. 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 The IBM 702 was an early generation electronic tube, tube-based digital computer produced by IBM in the early to mid-1950s. It was the company's response to Remington Rand's UNIVAC I, UNIVAC, which was the first mainframe computer to use magneti ...

. 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 The IBM 704 is the model name of a large digital computer, digital mainframe computer introduced by IBM in 1954. Designed by John Backus and Gene Amdahl, it was the first mass-produced computer with hardware for floating-point arithmetic. The I ...

and

IBM 709 The IBM 709 is a computer system that was announced by IBM in January 1957 and first installed during August 1958. The 709 was an improved version of its predecessor, the IBM 704, and was the third of the IBM 700/7000 series of scientific compute ...

. 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 The IBM 700/7000 series is a series of large-scale (mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s use vacuum-tube log ...

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 for the

IBM 7090 The IBM 7090 is a second-generation Transistor computer, transistorized version of the earlier IBM 709 vacuum tube mainframe computer that was designed for "large-scale scientific and technological applications". The 7090 is the fourth member o ...

and 7094 computer systems, was retained for the earliest System/360 systems as a

count key data Count key data (CKD) is a direct-access storage device (DASD) data recording format introduced in 1964, by IBM with its IBM System/360 and still being emulated on IBM mainframes. It is a self-defining format with each data record represented by a ...

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. Attachment to a 709x system is through an IBM 7909 Data Channel and an

IBM 7631 International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is a publicly traded company ...

File Control unit, which can attach up to five random-access storage units, a mix of 7320

1301 Year 1301 ( MCCCI) was a common year starting on Sunday of the Julian calendar. Events January– March * January 14 – With the death of King Andrew III ("Andrew the Venetian") after a short illness, possibly from poisoning, the � ...

, and

1302 Year 1302 ( MCCCII) was a common year starting on Monday of the Julian calendar. Events January–March * January 2 – In Germany, Henry II becomes the ruler of the independent nation of Mecklenburg (encompassing the modern-day nor ...

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 2,796 6-bit characters, and a 7320 unit holds 1,118,400 characters. Data transfer rate is 202,800 characters per second. 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 2,081 8-bit bytes, and a 7320 unit holds 878,000 bytes. Data transfer rate is 135,000 bytes per second. The 7320 was superseded by the

IBM 2301 In addition to the drums used as main memory by IBM in, 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 ...

in mid-1966.

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.

IBM 2303

The IBM 2303 is a magnetic drum storage device with the same physical specifications as the

. 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.

Notes

References

{{Reflist History of computing hardware 7320 Computer storage devices