Types of Computer Memory
In order for a computer to manipulate data, it has to have ways to store information. Modern computers generally have different systems that store memory, each serving a different purpose. Memory intended for storage, such as CDR, hard drives and flash memory, are effectively the long-term memory of a computer system. This memory is almost always non-volatile, meaning that when power is shut off, data is still preserved. Another form of memory is comparable to short term memory. RAM, or Random Access Memory, stores data temporarily for easy retrieval for processing. This memory is often volatile, only retaining its data structures as long as power is on.
When the term computer memory is used, it usually refers to computer RAM. This type of memory is a very popular choice for computer upgrades because it is easy to install and can offer very noticeable performance improvements. The amount of RAM and the speed it can be accessed at are both important factors in their impact on computer systems. The different types of RAM available throughout the history of computers have mainly differed in the technology they utilized to offer both more speed and more space. Today, with processors that are blazing fast and more low level cache being implemented directly on the processor itself, speed is the bottleneck that computer RAM has to confront.
Almost all modern main memory is a form of dynamic RAM, known as DRAM. This dynamic computer memory uses banks of transistors and capacitors to store data, with each transistor/capacitor pair storing one bit of information by either containing a charged or discharged capacitor. This technology is known as dynamic because during idle time the charge in the capacitors dwindles and has to be be recharged. This pairing of structures is fairly simple and allows for a very high density of memory to be etched onto a chip.
The predominant form of commercial computer memory is DDR SDRAM. All of these letters stand for double-data rate synchronous dynamic random access memory. DDR has gone through three generations of technological evolution to date, with a fourth set to debut by 2015.