Rambus on Alternate Platforms

Introduction

Due to its weakness in latency, the specific performance balance of Rambus DRAM does not seem to favor current generation uniprocessor desktop PC platforms running traditional applications. But, we should not assume that all CPUs, all platforms and all applications are the same or will be the same in the future. Beyond the mainstream PC platform, Rambus could provide a performance advantage for multiprocessor servers, IA64 systems, for graphics memory applications, for game consoles, etc. Also, depending on new CPU architectures and the evolution of application software, Rambus could become more interesting in the mainstream as well.

Under what circumstances could bandwidth be more important than latency?

There are many factors that will allow future systems to make more effective use of high bandwidth DRAM and help to compensate for latency problems. These include higher CPU bus speeds, deeper pipelining, speculative execution, explicit parallelism, etc. As next generation platform and CPU architectures penetrate the mainstream, increased bandwidth will be utilized much more effectively.

Will Rambus be popular for PC graphics accelerators?

There is no evidence yet. Earlier versions of Rambus DRAM have been used with the medium performance Cirrus Logic Laguna chip, and a commercially unsuccessful product from Chromatic. New Rambus designs will probably surface, but so far, the overwhelming trend is toward larger, wider, faster SDRAM configurations combined with DRAM integration strategies.

Is Rambus suitable for server applications?

It could be. In the future, Intel will offer Rambus server platforms and Compaq has announced plans for an Alpha server that uses Rambus (inherited from DEC). Rambus pipeline performance is a strong advantage for servers, but Rambus also introduces barriers pertaining to cost and maximum memory capacity. Current server platforms use very large configurations of inexpensive SDRAM. It will be challenging to support very large DRAM configurations with Rambus in the near term, plus many expect Rambus DRAM to be costly. Until these and other issues are resolved, there will be a near term preference for SDRAM on most server platforms.