Supplies and Comparisons

FiringSquad: There have been rumors that RDRAM yields have been very poor. Outside sources have given yield estimates in the 15-20% range. How are RDRAM yields?

There has been some confusion between wafer yields and speed yields. While wafer yields are comparable to SDRAM yields, the yields for PC800 may be in the 15-20% range at the start of production in the case of some manufacturers.

Today, there are three speed grades available, PC600, PC700 and PC800. Most DRAMs yield to one of the three speed grades. As production volumes ramp, the speed yields improve as well.

FiringSquad: Samsung is currently the only manufacturer making a significant amount of RDRAM. When will the other manufacturers begin ramping up RDRAM production? When does Rambus expect RDRAM to achieve price parity with SDRAM?

Since February, five DRAM suppliers have been validated and are all in production. We expect two additional suppliers to join their ranks in the second half of this year. In a commodity business like DRAMs, the highest volume component is the one that achieves the lowest price. As some point in time when RDRAM volume exceeds SDRAM volumes, SDRAM will cost more than RDRAM. This was true when memory transitioned from EDO to SDRAM.

FiringSquad: Who manufactures the RDRAM for the PlayStation2?

Toshiba currently manufactures the majority of RDRAMs for Sony's PS2.

FiringSquad: Did the PlayStation2 launch have any affect on RDRAM supplies?

No, the PS2 program was carefully planned over time. PS2 production volumes were estimated well in advance.

FiringSquad: What's the difference between RDRAM and normal DRAM? Is RDRAM just a normal DRAM with a Rambus interface?

In general the memory core is standard. Its high performance is due to the high-speed interface. From a manufacturing standpoint, RDRAMs look similar to any other DRAM with the exception of a high-speed interface.

From a systems standpoint, RDRAMs offer many additional advantages that traditional DRAMs cannot. The narrow high-speed interface allows high performance memory systems to be built out of far fewer DRAMs.

FiringSquad: How is Rambus better than DRAM?

First off, Rambus provides far higher bandwidth per pin than any other solution available today. This has many related benefits, the first is that high performance memory systems can be built from small numbers of RDRAMs. The PS2 for example, employs two Rambus channels each with a single RDRAM for a total of 3.2GB.

At the system level, the reduced pin count offered by RDRAMs results in fewer traces to route on the motherboard, fewer motherboard layers, and the ability to scale bandwidth by adding channels in parallel. These features allow price and performance to be balanced to meet the needs of a particular system.

As computing systems continue to undergo greater levels of integration, the high bandwidth and low latency of RDRAM will enable new computing paradigms or unified memory architecture (UMA) systems. A good example is the Nintendo 64, which used a previous generation Rambus product.