A claim added almost as an afterthought in a civil lawsuit filed last fall in Birmingham, Ala., paved the way for a broad antitrust suit that the Federal Trade Commission plans to file soon against Intel Corp..

The civil suit, accusing Intel of patent infringement, was filed in November by Intergraph Corp., a maker of computer work stations, which added to the suit at the last minute a claim of antitrust violation. Last month a federal judge concluded that there was a "substantial likelihood" that Intergraph would succeed in proving that claim. Now Intergraph's accusations may end up playing a central role in the trade commission's case.At issue, the government says, is that Intel, in retaliation for the patent infringement claim, refused to give Intergraph technical details of the Intel Pentium II processor that it needed to make its chips for the next generation of computers. Intel asserted a right to share information about its chips with whomever it pleased.

On April 10, Intergraph, which is based in Huntsville, Ala., won a preliminary injunction requiring Intel to continue supplying it with advanced product information, advanced microprocessor chip samples, early production chips and production chips. Intel has appealed but is complying with the injunction.

In the ruling, Judge Edwin Nelson of the U.S. District Court wrote that Intel was a monopolist in the microprocessor market and that it had engaged in practices aimed at extending that monopoly to other businesses.

In a telephone interview on Wednesday, James Meadlock, Intergraph's chairman and chief executive, said the disputed patents relate to technology used to keep the microprocessor's own internal memory, known as its cache, synchronized with a computer's main memory, or RAM.

Though Intergraph asserted its patent rights with a number of computer companies, including IBM, it did not initially challenge Intel. But Intel asked Intergraph on several occasions to relinquish the patent rights in return for access to new products and technology, Meadlock said.

Intel executives deny any wrongdoing and say the case arose after Intergraph asserted patent rights with a number of computer makers using Intel chips, who then sought indemnification from Intel.