IBM 9370

The IBM 9370 systems were "baby mainframe" midrange computers,[1] released 1986 at the very low end of, and compatible with System/370.


The announcement[2] described the IBM 9370 as a "super-mini computer" for commercial and engineering/scientific use—compact, rack-mounted, designed for an office environment, not needing a data center to be used.

At the time of announcement the systems were positioned between the IBM System/36 / IBM System/38 and the IBM 4300 series in performance.[3]

Intended to be sold in large amounts as departmental machines ("VAX killers"),[4] the 9370 initially suffered from lack of software and the failure of IBM to market it properly.[5] Nevertheless, the systems were popular at least with users actually needing System/370 compatibility while not wanting to accept the expense of a larger system (like e.g. smaller software houses) or with users (like some large IBM customers) preferring hierarchically structured distributed processing solutions rigidly managed by central communication controllers like IBM 37xx. By 1990 the 9370 line had around 6,300 installed systems and generated over 2 billion dollars in sales for IBM.[5]

While becoming part of the Enterprise Systems Architecture in 1988 ("ES/9370" like "ES/4300" and "ES/3090"), the 9370s weren't XA systems. In 1990 IBM announced the "ES/9000" series; the rack-mounted models 120-170 with 31-bit Enterprise Systems Architecture (ESA) and ESCON were the suggested upgrades for ES/9370 users.[6]


Initially, the lineup contained four models: 20, 40, 60, and 90.[NB 1]

The IBM 9370 was partially a replacement[7] for the also-not-so-successful IBM 8100 distributed processing engine.

High-level 9370 models were mentioned as a substitution[8] when low-level 4300 models were withdrawn from marketing 1987.

The 9370 evolved into ES/9370, which itself was complemented with, and later followed on by the ES/9221 in 1990.

Models and options

During the 9370s product lifecycle, several models have been available.

Early models

Model Model No. Level Memory (MB) I/O card slots DASD/Tape Controller Workstation Controller MVS/SP capability
20, 30 9373 low priced, entry level 4, 8, 16 7 1-2 2 no
40, 50, 55, 60 9375 mid-size 8, 16 17 1-4 2-4 larger Mod.60 only
80, 90 9377 highest (5x Mod.20) 8, 16 54 1-12 2-12 yes

The 9370 core was an IBM 801 CPU. All models included a floating point accelerator as well as a processor console to install, operate and maintain the system.

Each DASD/Tape Controller had eight device addresses and provided a data transfer rate of 3 MB. IBM 9332 (368 MB) and IBM 9335 (824 MB) DASD and IBM 9347 nine-track half-inch tape have been announced for the 9370s.

Each Workstation Controller could interface up to 32 IBM 3270 terminals / printers.

Software for all models included VM/SP+VM/IS, VSE/SP, and VM/SP+IX/370, while MVS/SP was only available for larger models.

Enterprise systems architecture models

An upgrade (Miscellaneous Equipment Specification, MES) was available which involved - among other things - replacing the 9332 FBA drives with CKD enabled DASDs.

In 1988, Distributed Processing Programming Executive DPPX/370 for ES/9370 was made available to customers wanting to migrate[9] from the IBM 8100 running DPPX.

The "Micro Channel 370" Models 010, 012, 014 (later 110, 112, 114) ES/9371 introduced in 1990 used the Micro Channel bus and a 386 CPU for input/output (I/O) processing. Additionally, a dual-processor model was offered, providing a second 386 CPU for DOS and OS/2 applications, implementing a high-speed link between the processors. With the models mentioned, APPC support was added, using LU6.2 based on SNA PU2.1.

See also


  1. initial product announcement


  1. David E. Sanger (October 8, 1986). "I.B.M.'s Overseas Sales Slowing; Stock Plunges". The New York Times. ...the introduction of a new series of small mainframe computers, called the I.B.M. 9370 Information System, that the company is counting on to revive its offerings in the midrange computer market.
  3. Network World article Dec.22, 1986 p.28
  4. Christine Winter (June 20, 1988). "New IBM Midrange To Debut". Chicago Tribune. The 9370, a midrange computer nicknamed the VAX-killer because it reportedly was designed to attack Digital`s stronghold, its VAX line...
  5. Hamilton, Rosemary (February 5, 1990). "IBM 9370 user survives battle of misconceptions". Computerworld. Retrieved February 22, 2013.
  6. IBM Corporation. "System/390 ES/9000 Processor characteristics". IBM Archives. Retrieved February 22, 2013.
  7. June 16th 1989 CW article mentioning 8100-9370 replacement (in German)
  8. Network World article Jun.29, 1987 p.27
  9. IEEE Xplore - Porting DPPX from the IBM 8100 to the IBM ES/9370

Further reading

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