IBM mainframes are large computer systems produced by IBM since 1952. During the 1960s and 1970s, IBM dominated the computer market with the 7000 series and the later System/360, followed by the System/370. Current mainframe computers in IBM's line of business computers are developments of the basic design of the System/360.
The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applications and a complete range of applications from small to large. The design distinguished between architecture and implementation, allowing IBM to release a suite of compatible designs at different prices. All but the only partially compatible Model 44 and the most expensive systems use microcode to implement the instruction set, featuring 8-bit byte addressing and binary, decimal and hexadecimal floating-point calculations.
The IBM System/370 (S/370) is a model range of IBM mainframe computers announced on June 30, 1970, as the successors to the System/360 family. The series mostly maintains backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the product announcement. In September 1990, the System/370 line was replaced with the System/390.
Disk Operating System/360, also DOS/360, or simply DOS, is the discontinued first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966. In its time, DOS/360 was the most widely used operating system in the world.
IBM manufactured magnetic disk storage devices from 1956 to 2003, when it sold its hard disk drive business to Hitachi. Both the hard disk drive (HDD) and floppy disk drive (FDD) were invented by IBM and as such IBM's employees were responsible for many of the innovations in these products and their technologies. The basic mechanical arrangement of hard disk drives has not changed since the IBM 1301. Disk drive performance and characteristics are measured by the same standards now as they were in the 1950s. Few products in history have enjoyed such spectacular declines in cost and physical size along with equally dramatic improvements in capacity and performance.
The IBM 4300 series are mid-range systems compatible with System/370 that were sold from 1979 through 1992. They featured modest electrical and cooling requirements, and thus did not require a data center environment. They had a disruptive effect on the market, allowing customers to provide internal IBM computing services at a cost point lower than commercial time-sharing services. All 4300 processors used a 3278-2A, 3279-C or 3205 display console rather than a 3210 or 3215 keyboard/printer console.
The IBM 3705 Communications Controller is a simple computer which attaches to an IBM System/360 or System/370. Its purpose is to connect communication lines to the mainframe channel. It was a first communications controller of the popular IBM 37xx series. It was announced in March 1972. Designed for semiconductor memory which was not ready at the time of announcement, the 3705-I had to use 1.2 microsecond core storage; the later 3705-II uses 1.0 microsecond SRAM. Solid Logic Technology components, similar to those in S/370, were used.
Since the rise of the personal computer in the 1980s, IBM and other vendors have created PC-based IBM-compatible mainframes which are compatible with the larger IBM mainframe computers. For a period of time PC-based mainframe-compatible systems had a lower price and did not require as much electricity or floor space. However, they sacrificed performance and were not as dependable as mainframe-class hardware. These products have been popular with mainframe developers, in education and training settings, for very small companies with non-critical processing, and in certain disaster relief roles.
The IBM System/360 Model 30 was a low-end member of the IBM System/360 family. It was announced on April 7, 1964, shipped in 1965, and withdrawn on October 7, 1977. The Model 30 was designed by IBM's General Systems Division in Endicott, New York, and manufactured in Endicott and other IBM manufacturing sites outside of U.S.
The IBM System/360 Model 67 (S/360-67) was an important IBM mainframe model in the late 1960s. Unlike the rest of the S/360 series, it included features to facilitate time-sharing applications, notably a Dynamic Address Translation unit, the "DAT box", to support virtual memory, 32-bit addressing and the 2846 Channel Controller to allow sharing channels between processors. The S/360-67 was otherwise compatible with the rest of the S/360 series.
The history of IBM mainframe operating systems is significant within the history of mainframe operating systems, because of IBM's long-standing position as the world's largest hardware supplier of mainframe computers. IBM mainframes run operating systems supplied by IBM and by third parties.
The IBM System/360 Model 50 is a member of the IBM System/360 family of computers. The Model 50 was announced in April 1964 with the other initial models of the family, and first shipped in August 1965 to the Bank of America.
Beginning with its 1964 System/360 announcement, IBM's mainframes initially accessed count key data (CKD) subsystems via a channel connected to separate Storage Control Units (SCUs) with attached Direct Access Storage Devices (DASD), typically a hard disk drive. This practice continued in IBM's larger mainframes thru IBM Z; however low end systems generally used lower cost integrated attachments where the function of the SCU was combined with that of the channel, typically called an Integrated File Adapter.
The IBM System/360 Model 25 is a low-end member of the IBM System/360 family. It was announced on January 3, 1968, 3 years before the IBM System/360 Model 22, as a "bridge between its old and new computing systems".
The IBM System/360 Model 85 is a high-end member of the System/360 family of computers, with many advanced features, and was announced in January 1968 and first shipped in December 1969. IBM built only about 30 360/85 systems because of "a recession in progress".
The IBM System/370 Model 165 were jointly announced June 30, 1970 as "designed for ... the Seventies." That same day IBM announced the 370/195. They were the first three models of the IBM System/370 line of computers.
The IBM System/370 Model 145 was announced September 23, 1970, three months after the 155 and 165 models. It was the fourth member of the IBM System/370 line of computers, and was the first IBM computer to use semiconductor memory for its main memory instead of magnetic core memory. It was described as being five times faster than the IBM System/360 Model 40. First shipments were scheduled for late summer of 1971.
The IBM System/370 Model 135 was announced March 8, 1971, the only 370 introduced that year. The 135 was IBM's fifth System 370, and it was withdrawn October 16, 1979.
The IBM 303X is a discontinued line of mainframe computers, the first model of which, the IBM 3033 Processor, nicknamed "The Big One", was introduced March 25, 1977.
