History of Computers - Double Data Rate Memory

From SJS Wiki
Jump to: navigation, search

Introduction

Double Data Rate Synchronous Dynamic Random Access Memory (DDR SDRAM) was first developed in 2000, but before DDR there were other types of memory. Synchronous Dynamic RAM (SDRAM) was developed in the early 1990s, which was a step beyond the earlier asynchronous DRAM because SDRAM allowed the memory to queue up one process while waiting for another to finish. Now we call this type of memory Single Data Rate SDRAM because it can transfer one word machine of data during one clock cycle. In 2000, DDR SDRAM was developed, vastly improving computers in a number of ways.

SDL725421723.jpg

Overview

DDR improved upon SDR by allowing double the data per clock cycle. In a single clock pulse, there is one word of data during the positive edge and one during the negative edge, which basically means that RAM can read and write simultaneously. The data bus transfer rate, therefore, is twice the clock frequency, so DDR-200 has a clock frequency of 100MHz.

SDR_DDR-302x175.jpg

Significance

Doubling the data bus transfer rate had a sort of domino effect on the rest of the computer. First, RAM could transfer data twice as fast. Because of the quicker speed, memory could run at a lower clock rate, which uses less energy and achieves faster transfer rates.

Laptop Revolution

A substantial improvement in laptops was not made until DDR 2 came out in 2003. DDR 2 improved speed even further, which again used less energy. Because memory used less energy, RAM produced less heat. Laptops no longer required fans allowing for smaller designs and had longer battery lives. The result is the revolution of laptops in the 21st century.

References

https://www.pcmag.com/article2/0,2817,2400801,00.asp

http://wccftech.com/history-ram-trip-memory-lane/

http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/dram/transform/