IBM 37xx (or 37x5) is a family of IBM

Systems Network Architecture Systems Network Architecture (SNA) is IBM's proprietary networking architecture, created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes formats and protocols but, in itself, is not a pi ...

(SNA) programmable communications controllers used mainly in mainframe environments. All members of the family ran one of three IBM-supplied programs. *''Emulation Program'' (EP) mimicked the operation of the older

IBM 270x 270x is a generic name for a family of IBM non-programmable communications controllers used with System/360 and System/370 computers. The family consisted of the following devices: * IBM 2701 Data Adapter Unit * IBM 2702 Transmission Control * I ...

non-programmable controllers. *'' Network Control Program'' (NCP) supported Systems Network Architecture devices. *''Partitioned Emulation Program'' (PEP) combined the functions of the two.

Models

370x series

* 3705 — the oldest of the family, introduced in 1972 to replace the non programmable

family. The 3705 could control up to 352 communications lines. * 3704 was a smaller version, introduced in 1973. It supported up to 32 lines.

371x

The 3710 communications controller was introduced in 1984.

372x series

The 3725 and the 3720 systems were announced in 1983. The 3725 replaced the hardware line scanners used on previous 370x machines with multiple microcoded processors. * The 3725 was a large-scale node and

front end processor A front end processor (FEP), or a communications processor, is a small-sized computer which interfaces to the host computer a number of networks, such as SNA, or a number of peripheral devices, such as terminals, disk units, printers and ta ...

. * The 3720 was a smaller version of the 3725, which was sometimes used as a remote concentrator. * The 3726 was an expansion unit for the 3725. With the expansion unit the 3725 could support up to 256 lines at data rates up to 256 kbit/s, and connect to up to eight mainframe channels. Marketing of the 372x machines was discontinued in 1989. IBM discontinued support for the 3705, 3720, 3725 in 1999.

374x series

* The 3745, announced in 1988, provides up to eight T1 circuits. At the time of the announcement IBM was estimated to have nearly 85% of the over US$825 million market for communications controllers over rivals such as NCR Comten and

Amdahl Corporation Amdahl Corporation was an information technology company which specialized in IBM mainframe-compatible computer products, some of which were regarded as supercomputers competing with those from Cray Research. Founded in 1970 by Gene Amdahl, a for ...

. The 3745 is no longer marketed, but still supported and used. * The 3746 "Nways Controller" model 900, unveiled in 1992, was an expansion unit for the 3745 supporting additional

Token Ring Token Ring network IBM hermaphroditic connector with locking clip. Screen contacts are prominently visible, gold-plated signal contacts less so. Token Ring is a computer networking technology used to build local area networks. It was introduc ...

and

ESCON ESCON (Enterprise Systems Connection) is a data connection created by IBM, and is commonly used to connect their mainframe computers to peripheral devices such as disk storage, tape drives and IBM 3270 display controllers. ESCON is an opt ...

connections. A stand-alone model 950 appeared in 1995.

Successors

IBM no longer manufactures 37xx processors. The last models, the 3745/46, were withdrawn from marketing in 2002. Replacement software products are Communications Controller for Linux on System z and

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Clones

Several companies produced clones of 37xx controllers, including NCR COMTEN and

References

37xx Computer networks 37xx 37xx {{Compu-stub