IBM System/370 Model 135

IBM System/370 Model 135

IBM System/370 Model 135
Announced Mar 8, 1971 and
withdrawn Oct 16, 1979
The following is the text of an IBM Data Processing Division technical press release distributed on March 8, 1971.

For many users of intermediate and smaller computers, the IBM System/370 Model 135, announced today, will provide economical and flexible entry into a wide range of advanced data base applications.

Among the factors significant to the Model 135's data base, teleprocessing and multiprogramming capabilities are:

Memory structure

The Model 135 is available in four main storage sizes, ranging from 96,000 to 240,000 bytes. Main memory has a read cycle of 770 nanoseconds and a write cycle of 935 nanoseconds. Each cycle moves two bytes at a time.

Microcode for system control functions and certain optional features is stored in a separate portion of memory called reloadable control storage (RCS), which supplements the Model 135's main memory. The standard 24,000-byte capacity of RCS can be expanded to 36,000 or 48,000 bytes, if needed to accommodate microcode for user-selected options such as extended precision arithmetic or emulation of the IBM 1400 series.

The microcode required for a specific Model 135 configuration is provided by IBM in a small disk cartridge. The contents of the disk are loaded into the RCS through a reading device located in the Model 135 console. Because the Model 135's control storage is reloadable, all microcode for a system need not reside in storage at all times, resulting in a more efficient use of control storage capacity.

System technology

The Model 135 uses the same innovative monolithic circuit memory introduced with System/370 Model 145 as well as monolithics throughout the central processor for all logic and arithmetic functions. In monolithic technology, microscopic components are diffused onto tiny silicon chips to form dense integrated circuits.

Use of monolithic circuitry contributes to the Model 135's high internal operating speed. Its basic machine cycle - - the time it takes to perform one microinstruction -- ranges from 275 to 1,430 nanoseconds, depending on the operation performed.

Integrated communications attachment

An optional integrated communications attachment (ICA) permits direct connection to the Model 135 of up to eight low- and medium-speed communications lines, used for linking terminals to the central processor. The ICA, a combination of microcode and circuitry in the central processor, eliminates the conventional need for a separate control unit, such as the IBM 2701 data adapter.

Communications with a wide variety of remotely located devices over private, leased or switched telephone lines is possible with the ICA. It performs the basic tasks of adapting transmission code to computer code, grouping signals from multiple lines for concurrent handling by a Model 135 multiplexer channel and controlling the flow of data to and from the computer.

Adapter features enable the ICA to handle any mixture of asynchronous or higher-speed binary synchronous communications lines. This means it can work with almost all the terminal devices offered by IBM, including the 1050, 2740 and 2780 communications terminals, the new 3735 programmable buffered terminal and the 2260 and 2265 display stations. The ICA also can provide communications to other IBM computers, including System/370, System/360 and System/3, when those processors are equipped with communications adapters.

Integrated file adapter

Low-cost disk storage is made available to Model 135 users by an optional integrated file adapter (IFA). This feature, introduced with System/370 Model 145, permits direct attachment of an IBM 2319 disk storage facility without the need for a separate disk control unit.

The 2319 contains three disk drives and provides up to 87-million bytes of on-line data storage. A 2319 and either a one-disk 2312 or two-disk 2318 drive can be operated with the Model 135's IFA, for a total capacity of about l45-million bytes. Using a separate control unit, the Model 135 can support up to three 2319s or any combination of 2312, 2318 and four-disk 2313 modules up to a maximum of nine drives.

High channel capacity

Either one or two high- capacity channels - - data paths between all system devices and the central processor - - can be used with the Model 135. They provide a maximum aggregate data transfer rate of about 2.4-million bytes a second, about four times that of System/360 Model 30.

Block multiplexing, previously available only with IBM's more powerful computers, permits each channel to operate multiple high-speed input and output devices concurrently under OS. This results in a significant increase in system throughput.

Large capacity channels permit Model 135 users to expand their multiprogramming operations and enable the new system to operate with IBM's newest and most advanced peripheral devices, including the 3330 disk storage, 3420 tape storage unit and 3211 high-speed printer.

The 3330 will operate with all System/370 models under DOS as well as OS, IBM announced today.

Programming support

Model 135 users will be able to run their System/360 applications under either OS or DOS without reprogramming. An OS/DOS compatibility feature, especially important to many intermediate and smaller system users, is standard with the Model 135. This enables programs written for DOS to be executed under OS, which has greater capability for data base and multiprogramming applications.

Model 135 installations will be able to use a number of IBM program products designed especially for data base and tele-processing applications. These include Information Management System/360 (IMS/360), Generalized Information System (GIS) and Customer Information and Control System (CICS), all of which assist in the creation, maintenance and use of a central data file.

Available as a no-charge option is integrated emulation of IBM's earlier 1400 series of computers. This permits programs written for IBM 1401, 1440 and 1460 systems to be run concurrently with System/360 and System/370 programs under either DOS or OS. Conventional stand-alone emulation requires a system to switch from its other work to handle programs written for earlier systems.

Additional machine highlights

As in all System/370 models, the Model 135 incorporates such advanced self-checking features as "CPU retry," which allows the computer to continue processing despite certain intermittent errors; error correction code circuits that automatically correct single-bit errors and detect all double-bit and most other multiple-bit errors; and program-assisted retry of channel errors.

Indicator lights behind a rotatable display on the Model 135's console face show the status of all critical points within the processor. Text written on the display enables an IBM customer engineer to determine quickly the general status of the machine as a basis for possible future diagnostic action.

Price summary

Monthly rental for typical configurations of IBM System/370 Model 135 will range from about $9,870 (with 96,000 bytes of main storage) to $22,600 (240,000 bytes). Purchase prices will range from about $475,000 to $1,068,000.

The integrated communications attachment will rent from $200 to $600 a month, depending upon the number of communications lines selected. Its purchase price will range from $9,880 to $29,650. The integrated file adapter, for use with the IBM 2319 disk storage, will rent for $475 a month, with a purchase price of $23,465.

First customer shipments of the Model 135 will be scheduled to begin in May, 1972.