Rambus Incorporated (founded 1990) is a provider of high-speed interface technology, most notably their Rambus Direct RAM memory technology, which was intended to replace SDRAM as the standard memory used in computers. In 1996, Rambus and the Intel Corporation signed an agreement that, in exchange for favorable license terms, Intel became obligated to use RDRAM as the primary memory technology of all Intel platforms until 2002.
Technology
The first PC motherboards with support for RDRAM debuted in 1999. They supported PC800 RDRAM, which operated at 800MHz and delivered 1600MB/sec of bandwidth over a 16-bit bus using a 184 pin RIMM form factor. This was significantly faster than the previous standard, PC133 SDRAM, which operated at 133Mhz and delivered 1066MB/sec of bandwidth over a 64-bit bus using a 168 pin DIMM form factor. Some downsides of RDRAM technology, however, included significantly increased latency, heat output, manufacturing complexity, and cost. PC800 RDRAM operated with a latency of 45ns, compared to only 7.5ns for PC133 SDRAM. RDRAM memory chips also put out significantly more heat than SDRAM chips, necessitating heatsinks on all RIMM devices. RDRAM also includes a memory controller on each memory chip, significantly increasing manufacturing complexity compared to SDRAM, which used a single memory controller located on the northbridge chipset. RDRAM was also two to three times the price of PC133 SDRAM due to a combination of high manufacturing costs and high license fees.
DDR SDRAM, introduced in 2000, operated at an effective clockspeed of 266MHz and delivered 2100MB/sec over a 64-bit bus using a 184 pin DIMM form factor. With the introduction of the i850 chipset, Intel added support for dual-channel PC800 RDRAM, doubling bandwidth to 3200MB/sec by increasing the bus width to 32-bit. This was followed in 2002 by the i850E chipset, which introduced PC1066 RDRAM, increasing total dual-channel bandwidth to 4200MB/sec. Also in 2002, Intel released the E7205 Granitebay chipset, which introduced dual-channel DDR support for a total bandwidth of 4200MB/sec, but at a much lower latency than competing RDRAM. In 2003, Intel released the i875P chipset, and along with it dual-channel DDR400. With a total bandwidth of 6400MB/sec, it marked the end of RDRAM as a technology with competitive performance.
Lawsuits
After presenting its technology under NDAs to all the current leading DRAM manufacturers in 1988 and 1989, Rambus was invited to join the Joint Electron Device Engineering Council, which was seeking to jumpstart innovation in future DRAM. During its participation in JEDEC, Rambus advocated a number of its technologies for use in future DRAM under then existing RAND licensing terms. During this time, Rambus never cast a vote to add any of its technologies to future standards. Rambus left JEDEC in 1996 after being prevented from formally presenting its technology for standardization by the JEDEC chair; the company was the only participant to be barred from making a formal presentation. From 1996 to 2000 Rambus advocated for the adoption of RDRAM as a new DRAM standard. During this time, a number of new DRAMs, including SDRAM, SLDRAM , and DDR SDRAM, were being marketed by companies who had signed NDAs with Rambus and were aware of the full extent of the technologies patented by Rambus. Rambus stated that it believed that each of these standards used a number of inventions from their 1990 patents. These patents contained multiple claims which were all, as required by law, present in their 1990 filings. Due to the US Patent Office requesting several divisions of the filing some of the inventions were not issued patents until 2000, though they all enjoy priority to the original 1990 filing in which they were contained.
In 2000, once the patents could be legally disclosed to the public, Rambus began discussing liscening terms with DRAM and memory controller manufacturers. Several of the largest manufacturers, including Samsung and Toshiba signed licenses, while Intel was already a licensee. Infineon, Micron and Hynix did not sign licenses and Rambus was forced to file suit to enforce their patents.
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