HP DL360 Memory technology evolution: an overview of system memory technologie - Page 2

Abstract Both the widening performance gap between processors and memory and the growth of memoryintensive 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. 2