RD RAM

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1. INTRODUCTION


One of the constants in computer technology is the continuing advancement in operational speed. A few years ago, a 66 MHz PC was considered “lightning fast”. Today’s common desktop machine operates at many times that frequency. All this speed is the foundation of a trend towards visual computing, in which the PC becomes ever more graphical, animated, and three- dimensional..

In this quest for speed, most of the attention is focused on the microprocessor. But a PC’s memory is equally important in supporting the new capabilities of visual computing. And commodity Dynamic RAMs (DRAMs), the mainstay of PC memory architecture, have fallen behind the microprocessor in their ability to handle data in the volume necessary to support complex graphics. While device densities have increased by nearly six orders of magnitude, DRAM access times have only improved by 10


2. RDRAM – WITH A DIFFERENCE

2.1 The Memory Landscape

Currently, there are three major groups of memory technology widely available in the market: Synchronous DRAM (SDRAM), Double Data Rate Synchronous DRAM (DDR SDRAM) and RDRAM memory. SDRAM and DDR SDRAM share many architectural and signaling features. Both use a parallel data bus, mainly available in component widths of x8 or x16, both have a single addressing command bus that must be shared to transmit row and column addresses.


Performance

Memory performance is usually summarized by two measures: bandwidth and latency. Peak system bandwidth can be defined as the maximum transfer rate of a particular memory technology given ideal conditions. Effects particular to each memory system degrade this peak bandwidth to a lower number called effective bandwidth. Effective bandwidth can be expressed as the product of peak bandwidth and efficiency, a measure of the ability of the memory system to deliver on its peak bandwidth given real world memory transaction patterns.