2.3. Memory in personal computers

The power of the computer depends on its architecture and is determined not only by the processor clock frequency. The performance of the systems is also affected by the speed of the memory and the bandwidth of the bus.

The organization of the interaction of the CPU and the OP depends on the computer's memory and chipset installed on the motherboard.

Storage devices are used to store information. Their functions include writing and reading it. Collectively, these functions are called memory accesses.

One of the most important characteristics of memory is the capacity and access time. Most often, the memory includes many identical storage elements. Earlier, ferrite cores were used as such elements, which were combined into a bit memory matrix. Currently, the memory elements of the OP are large integrated circuits (LSI).

When processing information by the processor, it is possible to refer to any OP cell; on the basis of this, it is called random access memory, or RAM. Typically, PCs have an OP that runs on dynamic-type chips, with cells assembled into a matrix.

In the static type of memory information is on static triggers. For static memory, no regeneration cycles and reloading operations are used, i.e., the access time to static memory is much less than to the dynamic one. The speed of the processor is highly dependent on the speed of the OP used. However, it affects the performance of the entire system. To realize one memory element of dynamic memory, 1–2 transistors are required, for static memory - 4–6, that is, the cost of static memory considerably exceeds the cost of dynamic memory. Based on this, a dynamic type RAM is most often used in PCs, and to increase system performance, it is super - operative, or cache memory. Surgical memory is made on the elements of the static type. In this case, the block of data processed by the processor is placed in the cache memory, but the access to the RAM occurs only when there is a demand for data that is not contained in the cache memory. The use of cache memory allows you to coordinate the speed of the processor and RAM on the elements of the dynamic type.

Integrated memory chips are produced in small quantities by Japanese, Korean, American and European companies.

Persistent storage devices, or ROMs, are designed to store the BIOS, which, in turn, ensures the invariance of software to the architecture of the motherboard. In addition, the BIOS contains the necessary set of I / O programs that provide peripheral devices.

In addition to the I / O programs, the ROM includes:

• test program when you turn on the computer POST;

• a bootloader program that performs the function of booting the OS from disk.

As a result of lower prices for reprogrammable ROMs, storage elements are used for storing BIOS, information in which can be erased electrically or with ultraviolet radiation. Currently, flash memory is most often used for these purposes , allowing you to make corrections to the BIOS.

PC memory
Computer memory is a set of devices for storing programs, input, intermediate results and output data. Memory classification is presented in Figure 1.

PC memory classification

Fig. 1 PC memory classification

Internal memory of the personal computer
Internal memory is designed to store relatively small amounts of information when processed by a microprocessor. It is volatile and non-volatile.

Volatile memory is memory that is erased when the computer is turned off. Non-volatile is called memory, which is not erased when you turn off the computer.

Non-volatile internal memory is a permanent storage device (ROM). The contents of the ROM is set at the factory and does not change in the future. This memory is made up of microcircuits, as a rule, of small volume. Usually, programs are written to the ROM that provide the minimum basic set of computer device control functions. When you turn on the computer, the original control is transferred to the program from the ROM, which tests the components of the computer and starts the operating system loader program.

volatile internal memory includes random access memory (RAM), video memory, and cache memory. In binary memory, the processed information, its processing program, intermediate data and work results are stored in binary form. RAM provides modes for writing, reading and storing information, and at any time it is possible to access any randomly selected memory cell. This is reflected in the English name of RAM - RAM (Random Access Memory - random access memory). Access to this information in the RAM is very fast. This memory is made up of complex electronic circuits and is located inside the computer case. Part of the RAM is allocated for storing images received on the monitor screen, and is called the video memory. The more video memory, the more complex and high-quality images can display a computer. High-speed cache memory is used to increase the speed of computer operations and is used when exchanging data between the microprocessor and RAM. The cache is an intermediate storage device (buffer). There are two types of cache memory: internal, located inside the processor and external, placed on the motherboard.