Rambus has produced what it believes is a smoking gun in its ongoing patent infringement court case with Hynix.

The court has ordered Hynix to produce a document allegedly revealing details of a secret DRAM manufacturers' cartel that Rambus claims was called "the JRA Group".

The court also ordered that Rambus be provided details of a joint defence agreement apparently entered into in August 2000 by several semi-conductor manufacturers, including three DRAM makers: Hynix; Micron; and Infineon.

Hynix has asserted that these documents are privileged and need not be produced under a joint-defense agreement. The documents apparently include communications between Hynix and its competitors regarding Rambus and its patents.

John Danforth, a senior VP and general counsel at Rambus, said: "While we cannot know the contents of the documents withheld on the basis of a claim of 'joint defense', they seem to show a high degree of co-operation among defendants relating to Rambus and its patents. The dates of these documents may also be significant. They predate the design of new DRAM products using Rambus technology and fall in a time period when, according to the recent guilty pleas of one DRAM company and four of its executives, there existed a criminal conspiracy among certain DRAM companies to eliminate competition."

Rambus designed RDRAM as an advanced memory technology in the early 1990s. However it claims that DRAM manufacturers conspired to keep RDRAM memory prices high whilst keeping prices of their preferred SDRAM chips lower. Rambus is pursuing lawsuits that assert these DRAM manufacturers unlawfully fixed DRAM prices and also infringed Rambus' patents since their SDRAM actually used Rambus technology. It wants to collect royalties for this use.

The pursued DRAM vendors say that when the SDRAM standard was defined Rambus did not inform the standard-setting committee that it had patent rights over certain technologies in the standard. In an earlier ruling in the Rambus/Hynix patent case, a judge made a summary judgment finding that Hynix's DRAM products infringed 29 of Rambus's patent claims.

Infineon recently pleaded guilty in an anti-trust case and agreed it had conspired with other DRAM manufacturers to fix prices in the July 1999 - June 2002 period. Four Infineon executives have been jailed for this.

Samsung has reportedly set aside $100 million to cover the potential costs of DRAM price fixing liabilities.

Rambus is also suing Hynix, Infineon, Inotera Memories, and Nanya Technology for infringement of its patents in the manufacture of DDR2 memory. It claims that they infringe up to 18 of its patents with DDR2, GDDR2 and GDDR3 devices that are currently shipping in the marketplace.

Samsung, not included in the DDR2 patent infringement case, is licensing Rambus technology for its XDR memory products.

The Hynix/Rambus case is set to start on 11 April.