IBM System/34

The IBM System/34 was an IBM midrange computer introduced in 1977.^[2] It was withdrawn from marketing in February 1985.^[2] It was a multi-user, multi-tasking successor to the single-user System/32. It included two processors, one based on the System/32 and the second based on the System/3. Like the System/32 and the System/3, the System/34 was primarily programmed in the RPG II language.^[3]

IBM System/34

IBM System/34 type 5340
Also known as	S/34
Manufacturer	International Business Machines Corporation (IBM)
Product family	System/34
Release date	April 1977; 48 years ago (1977-04)
Discontinued	February 1985
Operating system	System Support Program
CPU	MSP and CSP
Memory	48K – 256K
Dimensions	1220x660x1570mm [1]
Predecessor	IBM System/32
Successor	IBM System/36, IBM System/38
Related	IBM 5520
Website	"IBM Archives: System/34". Archived from the original on 2018-10-05.

Hardware

The 5340 System Unit contained the processing unit, the disk storage and the diskette drive. It had several access doors on both sides. Inside, were swing-out assemblies where the circuit boards and memory cards were mounted. It weighed 700 lb (320 kg) and used 220V power.^[4] The IBM 5250 series of terminals were the primary interface to the System/34.

Processors

S/34s had two processors, the Control Storage Processor (CSP), and the Main Storage Processor (MSP). The MSP was the workhorse, based on System/3 architecture; it performed the instructions in the computer programs. The CSP was the governor, a different processor with different RISC-like instruction set, based on System/32 architecture; it performed system functions in the background. The CSP also executed the optional Scientific Macroinstructions, which were a set of emulated floating point operations used by the System/34 Fortran compiler and optionally in assembly code.^[5] The clock speed of the CPUs inside a System/34 was fixed at 1 MHz for the MSP and 4 MHz for the CSP. Special utility programs were able to make direct calls to the CSP to perform certain functions; these are usually system programs like $CNFIG which was used to configure the computer system.

Picture of a System/34 showing the diskette magazine drive

Memory and storage

The smallest S/34 had 48K of RAM and an 8.6 MB hard drive. The largest configured S/34 could support 256K of RAM and 256MB of disk space. S/34 hard drives contained a feature called "the extra cylinder," so that bad spots on the drive were detected and dynamically mapped out to good spots on the extra cylinder. Disk space on the System/34 was organized by blocks of 2560 bytes.

The System/34 supported memory paging, referring to as swapping.^[6] The System/34 could either swap out entire programs, or individual segments of a program in order to free up memory for other programs to run.

One of the machine's most distinctive features was an off-line storage mechanism that utilized "magazines"—boxes of 8-inch floppies that the machine could load and eject in a nonsequential fashion.^[7][8][9]

Software

IBM System/34 with 5251 terminal (on top) and 5211 printer (right, with top opened)

Operating System

Main article: System Support Program

The System Support Program (SSP) was the only operating system of the S/34. It contained support for multiprogramming, multiple processors, 36 devices, job queues, printer queues, security, indexed file support. Fully installed, it was about 5 MB.^[10] The Operational Control Language (OCL) was the control language of SSP.

Programming

The System/34's initial programming languages were limited to RPG II and Basic Assembler^[11] when introduced in 1977.^[12] FORTRAN was fully available six months after the 34's introduction,^[7] and COBOL was available as a PRPQ.^[13] BASIC was introduced later.

Successor systems

The IBM System/38 was intended to be the successor of the System/34 and the earlier System/3x systems. However, due to the delays in the development of the System/38 and the high cost of the hardware once complete, IBM developed the simpler and cheaper System/36 platform which was more widely adopted than the System/38.^[14] The System/36 was an evolution of the System/34 design, but the two machines were not object-code compatible. Instead, the System/36 offered source code compatibility, allowing System/34 applications to be recompiled on a System/36 with little to no changes. Some System/34 hardware was incompatible with the System/36.

A third-party product from California Software Products, Inc. named BABY/34 allowed System/34 applications to be ported to IBM PC compatible hardware running MS-DOS.^[15][16]