IBM 3790
| Company type | Product |
|---|---|
| Industry | Computer hardware |
| Founded | 1974 |
| Founder | International Business Machines Corporation (IBM) |
| Products | Distributed computing system, programmable terminal system |
| Parent | IBM Data Processing Division |
The IBM 3790 Communications System, introduced in 1974 by IBM's Data Processing Division, represented one of the pioneering platforms in distributed computing. Intended primarily for branch locations, retail outlets, and subsidiary offices, it linked to central mainframes through IBM's Systems Network Architecture (SNA). Despite its role as a precursor to the IBM 8100—which brought notable advancements in distributed data processing—the 3790 was regarded by industry experts in 1979 as having achieved only limited success.
System description
IBM positioned the 3790 as "a programmable terminal system designed with operator usability in mind."
Components
This system accommodated:
- As many as 16 IBM 3277 display terminals
- A built-in floppy disk drive
- A line printer capable of producing 120 lines per minute (lpm)
- Up to three 3292 auxiliary control units
- Up to four 3793 keyboard-printers
- An interface based on Synchronous Data Link Control (SDLC) communications protocol
- An internal or external modem operating at 1200 baud
At its heart was the IBM 3791 programmable control unit, available in two configurations:
- Model 1 featuring 8.3MB of disk storage
- Model 2 offering capacity up to 26.9MB
Peripheral options comprised:
- The 3792 auxiliary control unit supporting
- Up to two dial-in IBM 2741 communication terminals
- Up to four 3793 display stations alongside a line printer
- As many as four 3793 printer-keyboards
- The 3411 Magnetic tape unit and controller (debuted in 1977), which could manage up to three 3410 tape drives
Host software
The system was compatible with several host software packages, including:
- Function Support Program
- Subsystem Support Services
- VTAM (operating on DOS/VS, OS/VS1, or OS/VS2 hosts)
- User Application Support Program
Reception
The IBM 3790 fell short of IBM’s anticipated performance due to multiple challenges. Its programming language, The 3790 Macro Assembler, necessitated development on an IBM mainframe before the compiled programs could be transferred to the device, complicating deployment procedures. Although aimed at mid-sized businesses as a departmental processing solution, reliance on a mainframe-based development environment hindered widespread acceptance. Furthermore, the system’s price point exceeded that of comparable minicomputers.
To aid programmers, IBM launched Program Validation Services (PVS), which enabled testing of applications on the mainframe through scripted procedures. However, generating these scripts was labor-intensive and prone to errors, while limited access to mainframe resources discouraged extensive use beyond initial program validation.
The Macro Assembler documentation was voluminous and challenging to consult efficiently. Developers faced difficulties managing code size and structuring programs effectively to prevent delays caused by the hardware’s memory architecture, which loaded segments in 2k increments.
In response, IBM developed DMS—an automated code generator later renamed Cross System Product (CSP) for the 8100 platform. DMS served as a screen painter facilitating straightforward tasks such as field validation and numeric checks; however, more complex programming still required use of the Macro Assembler.
IBM 3730
Launched in the late 1970s, the IBM 3730 was a word-processing adaptation of the 3790 hardware. It incorporated software customized for a dedicated shared-logic word-processing environment supporting twelve or more IBM 3732 terminals derived from the IBM 3270 series. Returned IBM 3777 terminals were modified with specialized word-processing keyboards and integrated into the 3730 system. Connectivity was maintained via Systems Network Architecture to a central mainframe running IBM DISOSS, a centralized document distribution system operating under CICS.
External links
- Overview of the IBM 3790 Communications System by IBM World Trade Corporation
- The Role of Insurance in the IBM 3790 Communications System (1974)