Draft Document for Review April 7, 2004 6:15 pm

6947glos.fm

Glossary

active configuration. In an ESCON environment, the ESCON Director configuration determined by the status of the current set of connectivity attributes. Contrast with saved configuration.

allowed. In an ESCON Director, the attribute that, when set, establishes dynamic connectivity capability. Contrast with prohibited.

American National Standards Institute (ANSI). An organization consisting of producers, consumers, and general interest groups, that establishes the procedures by which accredited organizations create and maintain voluntary industry standards in the United States.

ANSI. See American National Standards Institute.

APAR. See authorized program analysis report.

authorized program analysis report (APAR). A report of a problem caused by a suspected defect in a current, unaltered release of a program.

basic mode. A S/390 central processing mode that does not use logical partitioning. Contrast with logically partitioned (LPAR) mode.

blocked. In an ESCON Director, the attribute that, when set, removes the communication capability of a specific port. Contrast with unblocked.

CBY. Mnemonic for an ESCON channel attached to an IBM 9034 convertor. The 9034 converts from ESCON CBY signals to parallel channel interface (OEMI) communication operating in byte multiplex mode (Bus and Tag). Contrast with CVC.

chained. In an ESCON environment, pertaining to the physical attachment of two ESCON Directors (ESCDs) to each other.

channel path (CHP). A single interface between a central processor and one or more control units along which signals and data can be sent to perform I/O requests.

channel path identifier (CHPID). In a Channel Subsystem, a value assigned to each installed channel path of the system that uniquely identifies that path to the system.

Channel Subsystem (CSS). Relieves the processor of direct I/O communication tasks, and performs path management functions. Uses a collection of subchannels to direct a channel to control the flow of information between I/O devices and main storage.

channel. (1) A processor system element that controls one channel path, whose mode of operation depends on the type of hardware to which it is attached. In a Channel Subsystem, each channel controls an I/O interface between the channel control element and the logically attached control units. (2) In the ESA/390 architecture, the part of a Channel Subsystem that manages a single I/O interface between a Channel Subsystem and a set of controllers (control units).

channel-attached.(1) Pertaining to attachment of devices directly by data channels (I/O channels) to a computer. (2) Pertaining to devices attached to a controlling unit by cables rather than by telecommunication lines.

CHPID. Channel path identifier.

cladding. In an optical cable, the region of low refractive index surrounding the core. See also core and optical fiber.

CNC. Mnemonic for an ESCON channel used to communicate to an ESCON-capable device.

configuration matrix. In an ESCON environment, an array of connectivity attributes that appear as rows and columns on a display device and can be used to determine or change active and saved configurations.

connected. In an ESCON Director, the attribute that, when set, establishes a dedicated connection between two ESCON ports. Contrast with disconnected.

connection. In an ESCON Director, an association established between two ports that provides a physical communication path between them.

connectivity attribute. In an ESCON Director, the characteristic that determines a particular element of a port's status. Seeallowed, blocked, connected, disconnected, prohibited, and unblocked.

control unit. A hardware unit that controls the reading, writing, or displaying of data at one or more input/output units.

© Copyright IBM Corp. 2004

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990 specifications

The IBM 990 series, often referred to in the context of IBM's pioneering efforts in the realm of mainframe computing, represents a unique chapter in the history of information technology. Introduced in the late 1960s, the IBM 990 series was designed as a powerful tool for enterprise-level data processing and scientific calculations, showcasing the company's commitment to advancing computing capabilities.

One of the main features of the IBM 990 was its architecture, which was built to support a wide range of applications, from business processing to complex scientific computations. The system employed a 32-bit word length, which was advanced for its time, allowing for more flexible and efficient data handling. CPUs in the IBM 990 series supported multiple instructions per cycle, which contributed significantly to the overall efficiency and processing power of the machines.

The technology behind the IBM 990 was also notable for its use of solid-state technology. This provided a shift away from vacuum tube systems that were prevalent in earlier computing systems, enhancing the reliability and longevity of the hardware. The IBM 990 series utilized core memory, which was faster and more reliable than the magnetic drum memory systems that had been standard up to that point.

Another defining characteristic of the IBM 990 was its extensibility. Organizations could configure the machine to suit their specific needs by adding memory, storage, and peripheral devices as required. This modular approach facilitated the growth of systems alongside the technological and operational demands of the business environments they served.

In terms of software, the IBM 990 series was compatible with a variety of operating systems and programming environments, including FORTRAN and COBOL, enabling users to access a broader array of applications. This versatility was a significant advantage, making the IBM 990 an appealing choice for educational institutions, research facilities, and enterprises alike.

Moreover, the IBM 990 was engineered to support multiprocessing, which allowed multiple processes to run simultaneously, further increasing its effectiveness in tackling complex computing tasks.

In summary, the IBM 990 series represents a significant advancement in computing technology during the late 20th century. With a robust architecture, versatile configuration options, and a focus on solid-state technology, the IBM 990 facilitated substantial improvements in data processing capabilities, making it a cornerstone for many businesses and academic institutions of its time. Its impact can still be seen today in the continued evolution of mainframe computing.