IBM Series/1

The Series/1 was developed at IBM's Boca Raton. It was a highly real-time oriented minicomputer, and was used for device control and communication. The Operating System was EDX, which stands for Event Driven Executive, or RPS, which stands for Realtime Programming System. The machine uses EBCDIC character encoding internally, but ASCII-based remote terminals could be attached via an I/O card with an RS-232 interface. This made the Series/1 compatible with the IBM 3101/3151/3163 ASCII display terminals. This was a departure from other IBM mainframes that used the 3270 terminals using coaxial connections.

Models

There were a few configurations for the Series/1:

• Model 1 - 4952, model C processor
• Model 3 - 4953 processor
• Model 5 - 4955, model F processor

Later two more models were released:

• Model 4 - 4954 processor
• Model 6 - 4956 processor

Memory could be provided from 16kByte up to 128kByte.

Programming

The computer could be programmed using a dedicated EDL programming language, or more common languages like FORTRAN, Cobol, Pascal, and PL/I. Even though the system was underpowered by today's standards, it supported a multi-user operating environment u nder the RPS Operating System. The series/1 was also the first computer for which IBM supported Unix.

Applications and users

Customers included commercial, government and military users. Some major commercial users at the time included Kmart, State Farm Insurance, Best Western Hotels and the United States Marine Corps. The computer was discontinued in 1980 in favor of the more popular AS/400 system.

Use in the 21st century

In 2016 the United States Government Accountability Office produced a document that documented the use of legacy computer systems that were in need of replacement and upgrading. The document listed that the Air Force's Strategic Automated Command and Control System still uses IBM Series/1 computers to coordinate the operational functions of the US nuclear forces, such as nuclear bombers, intercontinental balistic missiles, and tanker support aircraft. The system still used 8" floppy disks at the time. In 2019 the Department of Defense completed the retirement of the 8" floppy disk drives with a secure solid state digital storage solution. The replacement was a Floppy Disk hardware emulation, and as of 2019 the Air Force was still using the IBM Series/1 computer...