IBM System/370 Model 115

IBM System/370 Model 115

IBM System/370 Model 115
Announced Mar 13, 1973 and
withdrawn Mar 9, 1981
The following is the text of an IBM Data Processing Division technical press release distributed on March 13, 1973.

The IBM System/370 Model 115, announced today, establishes new levels of efficiency and economy for a large number of computer users expanding into advanced on-line applications.

The Model 115's virtual storage capability, under IBM's Disk Operating System/Virtual Storage (DOS/VS), makes up to 16 million characters of disk storage available to the system as though it were part of main memory. Large-scale disk storage is provided by direct attachment of the newly-announced IBM 3340 direct access storage facility. This can make it easier for programmers to write advanced application programs and can allow more jobs to run concurrently on the system.

Compatibility features

The Model 115 is compatible with other System/370s and can provide the computing growth required by users with a need to develop on-line applications such as data entry, inquiry and remote computing.

The new system's size, low cost and compatibility features make it an ideal System/370 entry system for users of IBM's System/3, 1130 computing system and System/360 Models 20, 22 and 25. For those users, the Model 115 has a highly-compatible ASSEMBLER language capability and can run applications in the high-level languages - - RPG II, COBOL, FORTRAN and PL/1. An integrated Model 20 emulator is optionally available. The Model 115's DOS/VS control program requires little or no reprogramming of applications running under System/360's Disk Operating System.

Processor design advancements

A standard cathode ray tube operator's console replaces the familiar compute lights and dials. It can improve operator communications with the system by displaying data entered from the keyboard and by showing the system's internal status. The console can display 16 lines of data with 56 characters per line and can be used for application data entry and inquiry. An optionally-available console printer feature provides for integrated attachment of an IBM 5213 printer to provide a record of messages flashed on the system's video display console.

The new computer's central processing unit includes main memory, main storage controller and independent satellite processors. The satellite processors contain control storage and logic and provide for independent processing of program instructions, input/output functions and system diagnostics. This helps reduce contention among the various processing elements and improves overall system performance.

The satellite processors address the system's main memory through the main storage controller with a maximum data transfer rate of two million bytes per second.

A machine instruction processor analyzes and executes machine language instructions. A service processor provides control for the operator console and optional console printer and for the removable magnetic disk cartridge which supplies the system's reloadable control storage. It also continuously monitors the internal operations and status of the Model 115 and logs system status data for later use by IBM field engineers.

Integrated I/O capabilities

The design of the satellite input/output processors incorporates the integrated features that allow a wide range of peripheral devices to be attached to the Model 115 without separate data channels or control units -- and their associated costs.

The Model 115 uses a minimum of two directly-attached IBM 3340 disk drives. Up to four 3340 disk drives may be attached, providing nearly 280 million characters of on-line storage.

An optional integrated printer attachment permits use of the newly-announced IBM 3203 printer, with speeds of 600 or 1,200 lines per minute, or the IBM 5203 printer with a speed of 300 lines per minute.

Up to 12 communications lines, four bi-synchronous and eight start/stop, can be supported by the integrated communications adapter. This optional feature allows a user to connect a wide range of IBM terminals, making the Model 115's computing power economically available to remote locations.

Data storage flexibility is enhanced by the new system's ability to handle both the familiar 80-column card and the newer 96-column card. The optionally-available integrated card I/O attachment feature permits use of either the IBM 2560 multi-function card machine or the IBM 5425 multi-function card unit. The 2560 can read up to 500 cards per minute, punch 160 columns per second and print 140 positions per second. The 5425 has reading speeds up to 500 cards per minute and punching and printing speeds up to 120 cards per minute. The Model 115's 96-column card capability allows it to exchange data with an IBM System/3.

An optional byte multiplexer channel allows attachment of a variety of IBM peripheral devices, such as the 1419 magnetic character reader, 3270 information display system, 3740 data entry system and 3886 optical character reader. It also allows attachment of communications controllers such as the IBM 3704. Providing 32 subchannels, the multiplexer channel has data rates of 29,000 characters per second in burst mode and 19,000 per second in byte mode.

Additionally, an optional integrated magnetic tape adapter enables the Model 115 to operate with the IBM 3410/3411 magnetic tape subsystem. Up to six tape drives can be included with data rates of 20,000 (four-drive maximum), 40,000 and 80,000 characters per second.

Main storage

The Model 115 offers the smallest main memory size -- 65,536 characters of data - - in the System/370 line, but also is available with, or may be expanded to, 98,304 characters. High-density monolithic MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) technology is used in main memory. The Model 115 uses MOSFET memory chips holding 2,048 bits of data, twice as much as the original MOSFET introduced on IBM's System/370 Models 158 and 168. The new system's main storage has a cycle time of 480 nanoseconds (billionths of a second) for two bytes of information, more than seven times faster than the ferrite core storage used in the System/360 Model 20 submodel 4.

Depending on the instruction mix and program structure and size, the new system can achieve instruction execution rates approximately 1 to 1.5 times faster than the System/360 Model 22 and 1.5 to 3 times faster than the System/360 Model 25.

In addition to its main storage, the Model 115 contains a standard 20,000 words (22-bit words) of reloadable control storage. Reloadable control storage relieves main memory from many tasks by maintaining the microcode required to help run emulation programs, monitor system performance and execute on-line diagnostics and other vital system-related functions. It is loaded from a removable magnetic disk cartridge that makes it easier to add new features to the system.

Prices and availability

First customer shipments of the IBM System/370 Model 115 are scheduled to begin in the first quarter of 1974. Typical monthly rentals will range from $5,891 to $8,155. Portions of the system also are available under IBM's recently announced term lease plan which provides for a 48-month contract period. Purchase prices will range from $265,165 to $352,115.

The Model 115 will be manufactured at IBM's facilities in Poughkeepsie, New York. It was developed at IBM's laboratories in Boeblingen, Germany.