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IBM mainframes are large computer systems produced by IBM since 1952. During the 1960s and 1970s, IBM dominated the large computer market. Current mainframe computers in IBM's line of business computers are developments of the basic design of the IBM System/360.
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Computer operating systems (OSes) provide a set of functions needed and used by most application programs on a computer, and the links needed to control and synchronize computer hardware. On the first computers, with no operating system, every program needed the full hardware specification to run correctly and perform standard tasks, and its own drivers for peripheral devices like printers and punched paper card readers. The growing complexity of hardware and application programs eventually made operating systems a necessity for everyday use.
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.
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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 Count Area that identifies the record and provides the number of bytes in an optional Key Area and an optional Data Area. This is in contrast to devices using fixed sector size or a separate format track.
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In the original S/360 and S/370 architectures, each processor had its own set of I/O channels and addressed I/O devices with a 12-bit cuu address, containing a 4-bit channel number and an 8-bit unit (device) number to be sent on the channel bus in order to select the device; the operating system had to be configured to reflect the processor and cuu address for each device. The operating system had logic to queue pending I/O on each channel and to handle selection of alternate channels. Initiating an I/O to a channel on a different processor required causing a shoulder tap interrupt on the other processor so that it could initiate the I/O.
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270x is a generic name for a family of IBM non-programmable communications controllers used with System/360 and System/370 computers.
Attached Support Processor (ASP) was an implementation of loosely coupled multiprocessing for IBM's OS/360 operating system. IBM later changed the name to Asymmetrical multiProcessor but retained the acronym ASP.
Beginning with its 1964 System/360 announcement, IBM's mainframes initially accessed 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 System/370; 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/390 was the third generation of the System/360 instruction set architecture. The first ESA/390 computer was the Enterprise System/9000 (ES/9000) family, which were introduced in 1990. These were followed by the CMOS System/390 mainframe family in the mid-1990s. These systems followed the IBM 3090, with over a decade of follow-ons. The ESA/390 was succeeded by the 64-bit z/Architecture in 2000.
The IBM System/370 Model 115 was announced March 13, 1973[, at that time the low-end model of the System/370 line. It was promoted as "an ideal System/370 entry system for users of IBM's System/3, 1130 computing system and System/360 Models 20, 22 and 25."
References
- ↑ IBM System/370 Special Feature Description: Channel-to-Channel Adapter (PDF) (First ed.). IBM. March 1972. GA22.6983·Q.
- ↑ Enterprise Systems Architecture/390 Channel-to-Channel Adapter for the System/360 and System/370 I/O Interface (2nd ed.). International Business Machines Corporation. October 1991. SA22-7091-01.
- ↑ Enterprise Systems Architecture/390 ESCON Channel-to-Channel Adapter (1st ed.). International Business Machines Corporation. October 1990. SA22-7203-00.
- ↑ IBM Corporation (1968). IBM System/360 Model 65 Functional Characteristics (PDF). p. 10.
- ↑ IBM Corporation. "System/370 Model 158". IBM Archives. Retrieved January 7, 2014.
- ↑ Jensen, R.M. (1979). "A formal approach for communication between logically isolated virtual machines". IBM Systems Journal. 18 (1): 71–92. CiteSeerX 10.1.1.91.1907 . doi:10.1147/sj.181.0071.
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