Memory industry is one of the most dynamic electronics applications today. In recent years memory chips have advanced at a rapid pace, which led to a dramatic drop in price. The main factor which led to increased production is the number of requests for memory, which increased due to all programs that use more memory but also because of the advantage which RAM offer compared to other technologies for information storage. At the same time, new modules have been improved performance, decreased access times and increased speed fieldbus. All these features have been implemented due to several technical factors, one of them will be the development of processors that by increasing the frequency introduce the need for increased performance memories. RAM (Random Access Memory) is memory that can be read or written at random, thereby access to a single memory cell without this involving use of other cells. In practice it is the memory of the PC, it is useful for temporary data processing, then they need to be stored on media that does not depend directly on the power supply to maintain information. ROM is typically used to store the BIOS of a PC. In practice, with the evolution of PC memory this time suffered a series of changes that result by the user lash rewriting the BIOS. The goal obviously is to update the BIOS functions to adapt to the new requirements and achievements hardware or even to repair some imperfections operation.
For identifying and accessing memory cells, Computer they have a unique address for every cell. Identifying memory cell is done by sending the address, the BUS address the decoder address (consisting of decoders for line and column), it identifies memory cell corresponding to the address received and send its contents to the data interface and this May further, the data BUS. In general, memory cells can not be accessed individually, for this reason, constructive memory array is encapsulated in a chip. Memory chips are assembled on a memory module in number 8. They are connected to the address bus and the data. This achieves a virtual memory cell, consisting of 8 bits. Memory modules in turn are organized in memory banks, they are interconnected in the same way as chips.
The waiting time for performing all operations that provide the information necessary data interface for some time, which is identified by the name latency. So, for transmitting addresses between the CPU, chipset and memory using two clock cycles. To identify memory cell is undergoing two operations. Line identification matrix, we need 2 cycles, this period is called RAS to CAS delay and identifying the column which consumes about the same time as the first surgery. Computer Submission to the data interface and consume 1 cycle for the last surgery, and then transmitting data to the processor chipset, another 2 cycles. After providing the information, if the request issued by the processor is greater than the width of bus data, these words are transmitted to processor burst rate “burst mode” every clock cycle, this is possible thanks to an internal number that identify next column amplifier and transmit the content.