Industry executives close to the patent skirmish said Rambus is in the midst of negotiating separate licensing agreements with Advanced Micro Devices Inc. and x86-processor start-up Transmeta Corp., both of which have been heavy supporters of the double-data-rate SDRAM interface Rambus claims to own.

The move marks something of a shift for Rambus, which to date has spent most of its patent licensing efforts on landing contracts with DRAM suppliers.

One synchronous interface license holder, Hitachi Ltd., was sued by Rambus earlier this year over its support of the interface in both its DRAM and SuperH family of microprocessors. That case was dropped following an out-of-court settlement, and at the time, Rambus executives said their chief targets would remain in the DRAM sector.

In the interim, Rambus has signed deals with NEC Corp., Oki Electric Industry Co. Ltd., and Toshiba Corp. and has engaged in international court actions against three other DRAM suppliers -- Hyundai MicroElectronics, Infineon Technologies, and Micron Technology.

Lately, however, Rambus has broadened the scope of its patent campaign, in the last month looking to those processor makers that are aggressively supporting DDR SDRAM, according to sources.

Sources said Rambus is closely watching AMD, which shortly will introduce its high-end Athlon Thunderbird processor with DDR support. In addition to rolling out its own DDR-enabled chipset, AMD's Thunderbird will be supported by Taiwan's "Big Three" third-party chipset makers -- Via Technologies, Acer Laboratories Inc., and Silicon Integrated Systems.

Transmeta of Santa Clara, Calif., also attracted Rambus' attention when it unveiled its Crusoe MPU last year with support for both DDR and PC133 SDRAM.

Rambus refused to discuss its legal strategy, and a spokesman for Transmeta declined to comment. An AMD spokesman would say only that the company "as a Direct RDRAM licensee, does have discussions from time to time with Rambus. We can't characterize this discussion. We are aware of Rambus' intellectual-property portfolio."

What is a matter of record is Rambus' efforts to influence SDRAM adoption, particularly DDR SDRAM, by laying claim to the technology and seeking to impose royalties on its use. The company's stated motive is to charge higher fees for the interface in what observers say is an effort to goad the industry toward Direct Rambus DRAM, an internally developed chip-to-chip interface whose ownership is not in dispute.

Despite Rambus' actions, some analysts said the company is more interested in creating a revenue stream than using royalties to retard the adoption rate of DDR SDRAM. "Prolonged court suits will have negligible impact on the DDR ramp-up coming at the beginning of next year," said Sherry Garber, an analyst at Semico Research Corp. in Phoenix. "The market, not litigation, will determine how successful DDR will be."

Rambus traces its claims to an amended patent application, filed in 1996 and granted last year, relating to synchronous-memory and synchronous-logic interfaces used to connect processors and memory devices.

As a result, the company has sued DRAM makers Hyundai, Infineon, and Micron for patent infringement, and in turn has been countersued by Hyundai and Micron. A Rambus spokeswoman last week added greater weight to the outcome of the suits, saying that the company may refuse to license any of the three memory makers if it prevails in its court case.

Rambus has in fact set preliminary ground rules for establishing royalty payments from processor suppliers seeking to use its synchronous interface technology.

Both Hitachi and NEC Corp. agreed to license their respective microprocessors as part of an agreement that also included royalties for SDRAM. While the DRAM royalties are to be paid only until the end of the year, when Hitachi and NEC merge their DRAM design and marketing operations in a new joint venture called Elpida Memory Inc., the MPU licenses will remain in effect.

Terms of the processor-related agreements have not been disclosed. A spokesman for Elpida Memory declined to say whether the company is discussing a new SDRAM license with Rambus.

One major chip maker, Samsung Electronics Co. Ltd., said it has yet to be contacted by Rambus regarding a synchronous-interface license. Sources said this may be because Samsung is currently the only major producer of Direct RDRAM chips for the PC market Samsung and Toshiba also make custom Direct RDRAM chips for the Sony PlayStation II electronic-game console.