System/360 Model 44

IBM System/360 Model 44

IBM System/360 Model 44
Announced August 16, 1965 and
withdrawn September 24, 1973.

The following is the text of an IBM Data Processing Division press technical fact sheet distributed on August 19, 1965.

IBM System/360 Model 44 draws its special talent for scientific computing from a combination of fast parallel binary operations; short-, long-, and variable-length precision floating point arithmetic; and its FORTRAN programming support.

The speed and power of the Model 44 are evidenced in its one microsecond memory access time and its 32 data bit word parallel arithmetic and data paths. Also, the Model 44 has 16 general-purpose registers in which calculations can be handled at microsecond speeds or implemented in optional 250-nanosecond Solid Logic Technology circuits.

Key features of the Model 44 are:

An addition or subtraction in fixed-point arithmetic, performed in the optional high-speed general registers of the Model 44, takes 1.75 microseconds. These 16 registers are used as index and base registers, as accumulators for fixed point arithmetic, and for logical operations.

The Model 44's processor storage is integrated with the central processor unit. Three storage sizes are available:

  8,192 words 32,768 characters
  16,384 words 65,536 characters
  32,768 words 131,072 characters

All transfers of data are checked by the parity bit assigned to each character unit. The 32-bit words carry four parity bits.

Data channels and peripheral equipment

The flow of information between Model 44's processor and its input/output equipment is directed by multiplexer channels. Three in total can be attached: one standard speed and two high speed.

These channels, essentially subdivide themselves into a network of sub-channels, setting up a two-way flow of data between the processor and input/output devices.

The standard speed channel, handling up to 64 such devices as printers, card units and communication terminals, operates at 50,000 characters per second in the multiplex mode. The high-speed channel, which can address up to 64 devices such as tapes, disks and data acquisition units, operates at 200,000 characters a second.

In the burst mode, with a single device capturing the entire multiplexer channel, the rates between the two channels vary from 200,000 characters to 500,000 characters a second.

Among the systems and devices that can be attached to the Model 44 are:

Model 44 is both well suited as an instrument of research for scientific use and is compatible with other models in IBM's System/360 line.

Normally, the Model 44 uses an abridged set of System/360 instructions -- those associated with scientific operations. It can, however, with the addition of an Extended Instruction Set capability run programs interchangeably with Models 30, 40, 50, 65 and 75 if system configurations (memory capacity and peripheral devices) are comparable and the problem programs not time dependent.

Model 44 programs can - - in turn - - be run on other System/360s, through the Single Disk Storage Drive which contains Model 44 programming and which is available for Models 30, 40, 50, 65 and 75.

Programming support

Comprehensive scientific programming support is provided for the Model 44 including:

  1. a Basic Program package for card and tape configurations, including a tape FORTRAN compiler and library;

  2. a series of programs for the Integrated Single Disk Storage Drive, including a monitor to handle stacked job processing;

  3. a series of over 100 scientific subroutines - - instructions to the computer for solving countless numbers of problems common to science and industry - - contained in an application program entitled System/360 Scientific Subroutine Package.

The languages used in these programs are the Model 44 instruction set terminology and FORTRAN - - the standard scientific computing language.

Also included with the Model 44 are:

  1. the System/360 interrupt system which uses electronic circuitry to identify the cause of the interrupt and switch the processor to a control routine for servicing it;

  2. an interval timer which is used for such things as job accounting to interrupt and prevent a runaway job from gaining control of the system.