Abstract; Introduction; Basic Dram Operation - Compaq BL10e - HP ProLiant - 512 MB RAM Overview

Abstract

Both the widening performance gap between processors and memory and the growth of memory-
intensive business applications are driving the need for better memory technologies for servers and
workstations. Consequently, several memory technologies are on the market at any given time. HP
evaluates developing memory technologies in terms of price, performance, and backward
compatibility, and implements the most promising technologies in ProLiant servers.
This paper summarizes the evolution of memory technology and provides an overview of some the
newest memory technologies that HP is evaluating for servers and workstations. The purpose is to
allay some of the confusion about the performance and benefits of the dynamic random access
memory (DRAM) technologies on the market.

Introduction

Processors use system memory to temporarily store the operating system, applications, and data they
use and manipulate. Therefore, application performance and data reliability are intrinsically tied to
the speed and bandwidth of the system memory. Over the years, these factors have driven the
evolution of system memory from asynchronous DRAM technologies, such as Fast Page Mode (FPM)
memory and Extended Data Out (EDO) memory, to high-bandwidth synchronous DRAM (SDRAM)
technologies. Yet, system memory bandwidth has not kept pace with improvements in processor
performance, thus creating a "performance gap." If processor and memory performance continue to
increase at current rates, the performance gap between them will widen.
The processor-memory performance gap is important because the processor remains idle while it
waits for data from system memory. This performance gap prevents many applications from effectively
using the full computing power of modern processors. In an attempt to narrow the performance gap,
the industry vigorously pursues the development of new memory technologies. HP works with Joint
Electronic Device Engineering Council (JEDEC) memory vendors and chipset developers during
memory technology development to ensure that new memory products fulfill customer needs for
reliability, cost, and backward compatibility.
This paper describes differences in price, performance, and compatibility of DRAM technologies.
Some descriptions are very technical. For readers who are not familiar with memory technology, the
paper begins with a description of basic DRAM operation and terminology.

Basic DRAM operation

Before a computer can perform any useful task, it copies applications and data from the hard disk
drive to the system memory. Computers use two types of system memory—cache memory and main
memory. Cache memory consists of very fast static RAM (SRAM) and is usually integrated with the
processor. Main memory consists of DRAM chips on dual inline memory modules (DIMMs) that can be
packaged in various ways depending on system form factor.
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