In 1970, GE sold most of its computer business to Honeywell and in 1971, RCA sold its computing division to Sperry Rand. With only Burroughs, UNIVAC, NCR, Control Data, and Honeywell producing mainframes, people then talked, but by now in humorless, blistering criticism, of "IBM and the BUNCH."^[11] In April 1973 Honeywell v. Sperry Rand, a landmark U.S. federal court case, was decided. That decision invalidated the 1964 patent for the ENIAC, the world's first general-purpose electronic digital computer, thus putting the invention of the electronic digital computer into the public domain.

Most of those companies are now long gone as IBM competitors, except for Unisys, which is the result of multiple mergers that included Sperry Rand, UNIVAC and Burroughs, and General Electric, which has re-entered the business in recent years.^{[citation needed]} NCR and Honeywell dropped out of the general mainframe and mini sector and concentrated on lucrative niche markets, NCR's being cash registers (hence the name, National Cash Register), and Honeywell becoming the market leader in thermostats. The IBM computer, the IBM mainframe, that earned it its position in the market at that time is still growing today. It was originally known as the IBM System/360 and, in far more modern 64-bit form, is now known as the IBM System z10.

IBM's success in the mid-1960s led to inquiries as to IBM antitrust violations by the U.S. Department of Justice, which filed a complaint for the case U.S. v. IBM in the United States District Court for the Southern District of New York, on January 17, 1969. The suit alleged that IBM violated the Section 2 of the Sherman Act by monopolizing or attempting to monopolize the general purpose electronic digital computer system market, specifically computers designed primarily for business. Litigation continued until 1983, and had a significant impact on the company's practices. In 1973, IBM was ruled to have created a monopoly via its 1956 patent-sharing agreement with Sperry-Rand in the decision of Honeywell v. Sperry Rand, a decision that invalidated the patent on the ENIAC.

A key event at IBM in 1969 was the decision to "unbundle" software from hardware sales. See unbundling of software and services, below.

In 1970, IBM entered the office copier market, and was immediately sued by Xerox Corporation for patent infringement. Although Xerox held the patents for the use of selenium as a photoconductor, IBM researchers perfected the use of organic photoconductors which avoided the Xerox patents. The litigation lasted until the late 1970s and was ultimately settled. Organic photoconductors are now widely-used in office copiers.

The major technical development of the 1970s was IBM's System/370 series.

Between 1971 and 1975, IBM investigated the feasibility of a new revolutionary line of products designed to make obsolete all existing products in order to re-establish its technical supremacy. This effort, known as the Future Systems project, was terminated by IBM's top management in 1975, but had consumed most of the high-level technical planning and design resources during five years, thus jeopardizing progress of the existing product lines (although some elements of FS were later incorporated into actual products).