The letters RAM stand for “random access memory.” This memory is where your computer stores information about programs it is currently running. It is faster than writing and reading information from the hard drive because it has no physical components that need to move, just electrical signals. There are many different types of RAM and over time they have increased in speed and efficiency. There are two main types of RAM: volatile and non-volatile. Among volatile RAM, there are two subcategories: static and dynamic.
In RAM electrical signals are sent to individual memory locations on the RAM chip for future reading by the processor. If RAM is volatile that means that electricity must be supplied to the chip at all times in order to keep the information. Static RAM keeps this information in a series of transistors which remember the electrical signal given to them with just a standard power signal. Because of the complexity of this type of RAM it is usually more expensive, but there is less chance of information loss. The other great benefit of this type of RAM is its speed. Because of its higher cost but greater speed, the most common usage for this type of RAM is in something called the L2 cache. This is RAM that is kept in the processor itself for near instantaneous access to the memory, and it doesn’t have to be large so the cost is minimal.
Dynamic RAM is different from static RAM in that it needs to be refreshed. It uses small capacitors to hold information, and these capacitors will drain out if not refreshed (electricity reapplied) about every 15 nanoseconds. This slight loss in speed is made up for by the reduced cost of this type of RAM. It is the most common form of RAM used in computers today. The most used type is DDR2. DDR2 is the successor to DDR SDRAM (Double Data Rate synchronous Dynamic RAM). What DDR did was to increasing the timing accuracy of RAM synchronizing with the processor so that greater speeds could be achieved. DDR2 increased on this principle and double the speed again. The current cutting edge computer RAM is DDR3. This managed to double even the speed of DDR2. Unfortunately none of the DDR RAMs are compatible with each other and can’t replace each other in a computer unless specifically designed for it.
The last type of RAM is non-volatile. This is the most uncommon type of RAM because of the fact that it needs to have its own power source attached to the chip itself. This makes the chip bulkier and it needs to be replaced more often. However, this RAM does have certain applications. In situations where the data is absolutely essential, like certain military and scientific applications non-volatile RAM can allow the power of a computing unit to be interrupted, but be able to restart with all active programs intact.