The furore surrounding the computer memory market has intensified with Rambus filing an anti-trust lawsuit against four competitors, accusing them of banding together to eliminate competition.

The suit, filed in California, names Hynix, Infineon, Micron Technology and Siemens and accuses their executives of colluding to raise the price of Rambus' RDRAM by restricting output in order to kill its chances of becoming a mainstream memory technology.

Rambus' general counsel John Danforth explained the decision to file the lawsuit: "What led to this development was the quantity and quality of the evidence. We couldn't ignore our fiduciary responsibility to our shareholders."

The allegations stem in part from e-mail and other documents made public during the US Federal Trade Commission's (FTC) trial against Rambus, in which an FTC judge threw out a complaint alleging that Rambus had improperly deceived a standards-setting organisation into adopting its patented memory technology as part of the SDRAM standard.

The e-mails detailed conversations between DRAM vendors expressing their displeasure over Intel's decision to adopt RDRAM as the future memory technology for its products. Additional documents cited in Rambus' complaint show that the DRAM vendors plotted to undermine Rambus by collectively lowering production goals in order to create a supply glut and raise the price of RDRAM during the late 1990s.

Rambus' critics have said that the complexity of RDRAM chipsets and the high prices of the memory chips, as well as Intel's failure to deliver a working RDRAM chipset on time, helped seal RDRAM's fate and make SDRAM and DDR SDRAM the industry standards they are today.

The FTC has also appealed against its judge's decision to throw out the case against Rambus, arguing that the company stands to make up to $3 billion from its actions. Any decision in this case is likely to have a strong effect on Rambus' own lawsuit.

A spokesman for Infineon declined to comment on the anti-trust lawsuit. Representatives from Micron, Siemens, and Hynix were not immediately available for comment.

Rambus designed RDRAM as an alternative to conventional DRAM technology in the early 1990s. The company does not manufacture memory chips, but licenses its designs to companies such as the defendants in its case.

The lawsuit is also just the latest salvo in a legal saga that has stretched for years. Rambus claims that the SDRAM standard infringes on some of its patents, and has filed numerous lawsuits attempting to collect royalties from DRAM manufacturers that did not agree to license Rambus' technology. The DRAM vendors claim that Rambus failed to inform a memory standards-setting committee that it held patents on certain technologies that were under consideration for the SDRAM standard, in violation of that committee's rules.

Rambus has prevailed in two legal challenges so far, winning an appeal of a fraud verdict stemming from a trial in Virginia, and a dismissal of the FTC's complaint against the company. Separate litigation related to the Virginia case is pending against Infineon, and the lawyers for the FTC have filed an appeal to the full Commission in that case.

A separate US Department of Justice anti-trust investigation against the DRAM vendors is also under way.