Rambus has added Samsung to the long list of companies it is suing for patent infringement.

The memory maker has launched two separate actions against Samsung. The first adds it to a patent infringement lawsuit over DDR2 RAM and two related graphics memory technologies, GDDR2 and GDDR3 - a lawsuit Rambus launched against a number of other chips makers in January.

The second alleges that Samsung infringed Rambus patents for the SDRAM (synchronous dynamic RAM) standard used in the vast majority of the world's PCs, as well as for DDR DRAM chips and controllers, Rambus said.

Samsung had no immediate comment on Rambus' action but said it would issue a statement later.

Rambus designs memory interfaces that link memory chips to the rest of the PC system. DDR2, GDDR2 and GDDR3 are speedier versions of SDRAM that allow memory chips to run more reliably at speeds above 400MHz, and are expected to become mainstream memory technologies later this year.

In the January lawsuit, filed in the California, Rambus accused Hynix, Nanya, Inotera and Infineon of infringing its patents. It reached a settlement with Infineon in March and continues against the others. Infineon agreed to pay Rambus $5.85 million per quarter for patent licences.

The Samsung lawsuit comes after talks with Rambus over an existing licence broke down. "We have been very public over the last three quarters about Samsung not having a licence for DDR2 and we have been holding off action against both SDRAM and DDR. But there have been issues come up with DDR licences and we've extended our actions to cover DDR2," said a Rambus spokesman.