Big Iron

Why Trust Techopedia

What Does Big Iron Mean?

"Big iron" is slang for an extremely large, expensive and fast computer. It often refers to oversized computers such as Cray’s supercomputer or IBM’s mainframe. The term originated in the 1970s, when smaller computers known as minicomputers were introduced. The term “big iron” was coined by users, and the industry, to differentiate large computers from the smaller minicomputers.


Originally, the phrase 'big iron' probably originates from early mainframes, which were very large computers with superior capabilities enclosed in room-sized metal frames. Historically, these big machines were used for centralized computing, while today they are used to serve hundreds — sometimes thousands — of users simultaneously, as well as smaller servers in a computing network.

Today, big iron computers are high-performance rigs primarily used by large companies for large-scale computing purposes, such as, for example, processing massive amounts of data generated by bank transactions. They are designed with considerable internal memory, a large amount of external storage, top-quality internal engineering, superior technical support, fast throughput, fast input/output and high reliability.

Techopedia Explains Big Iron

The term is a derivative of “iron,” which is used to refer to something sturdy, strong and tough. The term “big iron” is frequently applied to highly effective computer ranches and servers that have resilient steel stands.

In the 1960s and 1970s, the market for mainframes, or big iron, was mainly through the companies:

  • IBM
  • General Electric
  • RCA Corp.
  • Honeywell International Inc.
  • Burroughs Corporation
  • Control Data Corp.
  • NCR Corp.

The first big iron computer arguably is the UNIVAC I, a data-processing computer that replaced that era’s punch-card accounting machines. Much faster than its counterparts, it was considered “small” by that age’s standards, occupying a mere 14.5 × 7.5 × 9 feet (roughly 4.4 × 2.3 × 2.7 meters) of space.

Later servers based on the microcomputer design, or “dumb terminals,” were developed to cut costs and create greater availability for users. The dumb terminal was eventually replaced by the personal computer (PC). Subsequently, big iron came to be used mostly by government and financial institutions.

Despite tech experts in the early ‘90s predicting that big iron would eventually become extinct (hence the additional nickname of “dinosaurs”) by the end of that decade, large mainframes were overhauled again in subsequent years. In 2008 IBM released the z10 mainframe by updating the software and using low-cost microprocessors as the computing engine. Big iron machines are still appreciated today by government agencies and large corporations that need a secure and reliable computer for storing critical data, as well as running critical processes and transactions.

Big iron is, in any case, much smaller than it used to be. While old mainframes could occupy several thousand square feet, current ones are still much bigger than a traditional computer, but no larger than a big refrigerator.


Related Terms

Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.