The computer memory industry is one of the most dynamic of today’s world, especially if you talk about electronics. In recent years, the memory chips have advanced at a rapid pace, which led to a dramatic drop in the price per MB. The main factor that led to an increased production is the demand for more memory, which has increased because of all the programs that use a great amount of memory. This has lead to an advantage (from the point of view of performance) because now RAM has to offer more in comparison with other technologies for information storage.
Meanwhile the new modules have been improved in terms of performance, have decreased their access times and increased the bus speed. All these features have been implemented because of several technical factors, one of them being the evolution of processors, which have also a high speed. By increasing the need for more memory, the computer needs a better CPU and so on. Anyway, this is good, because this leads to performance.
The memories have been designed over time using many technologies, of which only some have managed to impose themselves on the market. The main reason for this, is of course the price compared to the performance the memory brings.
Further, in this article we propose a brief description of the memory functions for the most widespread memory types on the market, as well as the advantages and also disadvantages of the existing technologies. We start with the classification of the memories. The computer memories are classified into two categories. ROM (Read Only Memory) is a type of memory that cannot be rewritten or erased. The main advantage is that the memory is insensitive to electric current. The memory contents are preserved even when the computer is not powered. RAM (Random Access Memory) is a memory that can be read or written randomly, in this way you can access only a memory cell without this to involve the use of other cells. In practice it is the memory of your PC, it is useful for processing temporary data, data that do not need to be stored (saved) on a support which does not depend directly on energy supply to maintain the information.
The ROM memory is typically used to store the BIOS (Basic Input Output System) of a PC. In practice, with the evolution of the PC memory, the computers themselves have undergone through a series of changes that resulted in rewriting or burning the “Flash” memory by the user of the BIOS. The goal, obviously, is to update the BIOS functions to adapt to the new hardware requirements and achievements, or to fix some imperfections of the operation. So today there are many of such programmable ROMs (PROM, EPROM, EEPROM) through various techniques, more or less advantageous depending on the complexity of their operation.
BIOS is a program of small size (<2MB) without which the computer cannot run, it is the interface between the system components and the operating system (OS). RAM is classified as SRAM (Static) and DRAM (Dynamic). SRAM, this type of memory is used in memory cell structure, having four transistors and two electric cells. Changing the status from 0 to 1 is achieved by switching the transistor’s state. When reading a memory cell, the information is lost, because when using the matrix with transistors, the switching between the two states is very fast.
DRAM is basically the constructive memory cell which consists of one transistor and one electric cell. Changing the state is by charging and discharging. At each reading of the cell, the capacitor is discharged. This method is named “destructive reading”, because the memory cell must be recharged after each reading. Another problem, which reduces the overall performance, is referring to the time the memory needs to refresh, which is a mandatory procedure and takes place every 64 ms. The refresh of the memory is a consequence of the principle of operation of the capacitors. They collect the electrons that are moving between voltages, but after a certain period of time the energy stored decreases in intensity due to dielectric losses. These technical problems lead to an increased waiting time (latency) for the use of memory.
