What is the role of RAM?
The purpose of RAM (acronym for Random Access Memory) is to temporarily store data so that the processor can access it quickly. This volatile memory indeed has access times which are counted in nanoseconds, times much greater than those of a hard disk or an optical medium such as DVD or CD-ROM. It’s a bit short-term memory of your PC, HDD and SSD being rather long term.
The acronym for RAM is misleading because “random” access does not mean random, quite the contrary. Hence the term sequential memory sometimes used because the information is perfectly organized and stored in a RAM module but accessible at any time and in any order.
This volatile aspect is fundamental. Especially since, as soon as the data capacity of the memory, expressed in gigabytes, is full, the processor processes the stored information to integrate new ones from the hard disks which slow it down. The quantity but also the quality of the memory ( see the characteristics chapter ) must, therefore, be considered together.
The different versions and developments of PC memory
There is not a computer memory but computer memories!
The term RAM or random access memory has long been opposed to ROM (Read-only Memory) or read-only memory, the latter designating non-volatile storage. In case you have some specific like best RAM for i7 8700k are also available, because gaming passionate want more speed while enjoying PC games.
If the term ROM has become rare, the RAM family remains numerous. A distinction is thus made between static (SRAM) and dynamic (DRAM) random access memory. Less bulky, cheaper but also slower, DRAMs are the ones that equip our computers today.
But even within DRAM, there is a split, with one on one side DDR-SDRAM (or DDR for Double Data Rate Synchronous Dynamic Random Access Memory) and on the other SDRAM.
The first type indicates that at equal frequency, this type of memory doubles the transfer rate of reads / writes compared to conventional SDRAM. This is synchronous, that is to say that its frequency is synchronized with that of the system bus, as opposed to asynchronous memories, which have their own clock but require a short waiting time. due to synchronization with the system bus.
It was with Intel’s Northwood architecture in 2002 that DDR-SDRAM appeared, which has since undergone 3 major developments to increase data throughput from the original 200 to 400 MT / s.
DDR2-SDRAM is the second generation of DDR memory. The principle of naming is to show well the doubling of the theoretical flow at equal real frequency. Indeed the DDR2 memory has the same clock frequency as the DDR but thanks to a doubled bus frequency, the memory has a theoretical bit rate also doubled.
DDR3-SDRAM, the third generation of DDR memory, hit the market in late 2007 and provides twice the speed of DDR2.
The fourth and current generation of DDR memory, born at the end of 2014, is called… (drum roll)… DDR4 !! And guess what? It provides twice the speed of DDR3.