Computer memory and its varieties. Role of the hard drive

Introduction

Computer memory is one of the most important issues in the design of a computer, since it is the most important part of its design, namely, computer memory provides support for one of the most important functions of a modern computer - the ability to store information for a long time.

Together with the central processor, the storage device is the key link.

All personal computers use three types of memory: RAM, permanent memory and external (various storage devices).

Computer memory is also classified according to various criteria.

In this paper, we will consider the concepts of computer memory, its types and classifications in theoretical and practical contexts.

Personal computer memory. Basic Concepts

Computer memory (information storage device, storage device) is a part of a computer, a physical device or medium for storing data for a certain time. The operation of a storage device can be based on any physical effect that brings the system to two or more stable states. In modern computer technology often used physical properties semiconductors, when the passage of current through the semiconductor or its absence is interpreted as the presence of logical signals 0 or 1. Stable states determined by the direction of magnetization make it possible to use a variety of magnetic materials for data storage. The presence or absence of charge in the capacitor can also be used as a basis for the storage system.

Computer memory provides support for one of the the most important functions modern computer - the ability to store information for a long time. Together with the central processor, the storage device is the key link.

Information storage system in modern digital computer based on the binary number system. Numbers, text information, images, sound, video and other forms of data are represented as sequences of bit strings or binary numbers, each consisting of the values 0 and 1. This allows the computer to easily manipulate them, provided the storage system has sufficient capacity. For example, to store a short story, it is enough to have a memory device with a total capacity of only about 8 million bits (about 1 Megabyte).

To date, many different devices have been created for storing data, many of which are based on the use of a variety of physical effects. Universal solution does not exist, each contains certain shortcomings. That's why computer systems are usually equipped with several types of storage systems, the main properties of which determine their use and purpose.

The most familiar means of machine data storage used in personal computers are: modules random access memory, hard drives (hard drives), floppy disks (floppy disks), CDs or DVDs, as well as flash memory devices.

Types of personal computer memory

Computer memory comes in two types: internal and external. Internal memory consists of microscopic cells, each of which has its own unique address, or number. An element of information is stored in memory with a certain address assigned to it. To find this information, the computer “looks” into the cell and copies its contents to its “command” point. Capacity separate cell memory is called a word. Typically, a word length for a personal computer is 16 binary digits, or bits. A length of 8 bits is called a byte. Typical large computers operate on words of 32 to 128 bits (4 to 16 bytes) in length, whereas minicomputers deal with words of 16 to 64 bits (2 to 8 bytes). Microcomputers typically use words of length 8, 16, or 32 bits (1, 2, or 4 bytes, respectively).

There are two main classes internal memory : random access memory (RAM) and read only memory (ROM).

RAM work quickly: the microprocessor can access them in 10–20 ns. Typical commercial RAM modules store up to 256 MB (1 MB equals 1,048,576 bytes). RAM is reliable and lasts for years, performing billions of operations. RAMs only remember what you last told them; everything else is erased. When the power is turned off, the RAM loses its memory. RAM stores programs and data during operation. RAM is often thought of as temporary storage because data and programs are only stored in it when the computer is turned on or until the reset button is pressed. Before turning off or pressing the reset button, any data changed during operation must be saved to a storage device that can store the information permanently (usually a hard drive). When the power is turned on again, the saved information can be loaded into memory again.

The term RAM often refers not only to the chips that make up the memory devices in a system, but also includes concepts such as logical mapping and layout. Logical mapping is a way of representing memory addresses on the actual installed chips. Accommodation- this is the location of information (data and commands) of a certain type at specific system memory addresses.

The computer's central processing unit is connected to the RAM. The component's main RAM is useful for storing data and programs that run on the central processing unit. In modern computers, RAM, like solid-state memory, is attached to the central processing unit and uses the memory bus. The memory bus is also called the address bus. In addition to RAM, there is also cache memory , which contains small pieces of memory for use by the central processor. The goal is to reduce fetch time, and thus speed up the CPU. Cache memory increases the performance of the central processor, thereby affecting the operation of the computer. In general, RAM is the most important part of computer memory. RAM is made from integrated semiconductor chips.

Of course, the more RAM a personal computer has, the greater its ability to accommodate and use programs and data in its work. To increase the amount of RAM, additional memory (ExpandedMemory) is used on additional boards, as well as extended memory (ExtendedMemory), which is usually located directly on the motherboard. When working with additional memory, the processor accesses data as if it were located in regular RAM up to 1 MB, but it is redirected to additional memory on additional fee, which can have a capacity of several megabytes. To work with extended memory, the processor must switch from real mode to protected mode.

ROM he remembers it almost forever. ROMs are especially useful for tasks that require the same set of instructions to be repeated over and over again. ROMs usually work slower than RAM, but their memory is permanent and noise-resistant. Not all ROMs have absolutely permanent memory. Some ROMs have, so to speak, semi-permanent memory, that is, they remember (even when the power is turned off) what they were told until they are erased and rewritten. Erasing is accomplished by exposing the chip to high-intensity ultraviolet rays or other means, as in some modern erase-write memory chips.

External Memory is usually located outside the central part of the computer. Since external memory is slower than internal memory, it is used mainly for storing information that the computer does not urgently need. To use external memory, the computer’s “command post” usually transfers the desired contents of a portion of the external memory to the internal memory. Inner memory limited in volume, so computer designers strive to store as much information as possible in external memory.

External memory includes various magnetic media (tapes, disks), optical disks. External memory is cheaper than internal memory, but its disadvantage is that it is slower than internal memory devices.

Magnetic tapes Many people are familiar with audio and video cassette tapes as external memory devices. Both of them store analog data, i.e. signals that change continuously. This is a relatively cheap and rather slow medium.

Flexible magnetic disk is a small, thin and flexible plastic disk with a magnetic coating on one or both sides. The coated disk is enclosed in a protective sleeve or shell that has openings for access by the read/write head and drive motor. Like magnetic tape, a floppy disk can form a permanent record of a program or data because it is erasable and its contents can be changed.

HDD similar to flexible, but made of strong and rigid materials. It can spin faster and hold more information. Typical hard disk drive A drive for a personal computer is almost the same size as a floppy disk drive, but the capacity of a modern hard drive reaches 25–50 GB, that is, thousands of times more than a floppy drive. In addition, hard drives communicate with your computer much faster than floppy disks. A search that takes up to several seconds on a floppy disk takes only hundredths of a second on a hard drive. The hard drive in most computers serves as an external storage device for current recordings and application software.

Computer memory comes in two types: internal and external. Internal memory consists of microscopic cells, each of which has its own unique address, or number. An element of information is stored in memory with a certain address assigned to it. To find this information, the computer “looks” into the cell and copies its contents to its “command” point. The capacity of an individual memory cell is called a word. Typically, a word length for a personal computer is 16 binary digits, or bits. A length of 8 bits is called a byte. Typical large computers deal with words of 32 to 128 bits (4 to 16 bytes) in length, while minicomputers deal with words of 16 to 64 bits (2 to 8 bytes) in length. Microcomputers typically use words of length 8, 16, or 32 bits (1, 2, or 4 bytes, respectively).

There are two main classes internal memory : random access memory (RAM) and read only memory (ROM).

RAM work quickly: the microprocessor can access them in 10-20 ns. Typical commercial RAM modules store up to 256 MB (1 MB equals 1,048,576 bytes). RAM is reliable and lasts for years, performing billions of operations. RAMs only remember what you last told them; everything else is erased. When the power is turned off, the RAM loses its memory. RAM stores programs and data during operation. RAM is often thought of as temporary storage because data and programs are only stored in it when the computer is turned on or until the reset button is pressed. Before turning off or pressing the reset button, any data changed during operation must be saved to a storage device that can store the information permanently (usually a hard drive). When the power is turned on again, the saved information can be loaded into memory again.

Of course, the more RAM a personal computer has, the greater its ability to accommodate and use programs and data in its work. To increase the amount of RAM, additional memory (Expanded Memory) is used on additional boards, as well as extended memory (Extended Memory), which is usually located directly on the motherboard. When working with additional memory, the processor treats data as if it were located in regular RAM of up to 1 MB, but it is redirected to additional memory on an additional card, which can have a capacity of several megabytes. To work with extended memory, the processor must switch from real mode to protected mode.

External Memory is usually located outside the central part of the computer. Since external memory is slower than internal memory, it is used mainly for storing information that the computer does not urgently need. To use external memory, the computer's "command post" usually transfers the desired contents of a portion of the external memory to the internal memory. Internal memory is limited in capacity, so computer designers strive to store as much information as possible in external memory.

External memory includes various magnetic media (tapes, disks), optical disks. External memory is cheaper than internal memory, but its disadvantage is that it is slower than internal memory devices.

HDD similar to flexible, but made of strong and rigid materials. It can spin faster and hold more information. A typical hard disk drive for a personal computer is almost the same size as a floppy disk drive, but the capacity of a modern hard disk reaches 25-50 GB, that is, thousands of times more than a floppy disk. In addition, hard drives communicate with your computer much faster than floppy disks. A search that takes up to several seconds on a floppy disk takes only hundredths of a second on a hard drive. The hard drive in most computers serves as an external storage device for current recordings and application software.

Optical disc resembles both a magnetic disk and a gramophone record. There are CD-ROM discs - discs with write once, they cannot be erased or overwritten.

Later, rewritable laser discs were invented - CD-RW. On them, as on magnetic media, stored information can be erased and recorded again.

Laser discs such as DVD-ROM and DVD-RW video discs have the greatest information capacity among removable media. The amount of information stored on them can reach tens of gigabytes. Video discs contain full-length video films that can be viewed on a computer, just like on TV.

The most famous and convenient is flash memory, which is not only completely non-volatile, but can also contain an operating system and some application programs.

Computer memory is classified according to other parameters.

For available data operations:

¦ Read-only memory (ROM);

¦ Read/write memory.

By energy dependence:

¦ Non-volatile memory;

¦ Volatile memory:

Statistical memory (volatile memory, which only needs to maintain the supply voltage to store information);

Dynamic memory (volatile memory in which information is destroyed over time, and, in addition to supplying power, it is necessary to periodically restore it).

By sampling order:

¦ with sequential access (SAM) - when memory cells are selected (read) sequentially, one after another, in the order of their location;

¦ random access (RAM) - when computing device can access an arbitrary memory cell at any address.

By purpose:

¦ Buffer memory- memory designed for temporary storage of data when exchanging it between various devices or programs;

¦ Temporary (intermediate) memory - memory for storing intermediate processing results;

¦ Cache memory is a part of the device or software architecture that stores frequently used data to make it available more quickly. fast access, rather than cached memory;

¦ Corrective memory is a part of the computer memory designed to store the addresses of faulty main memory cells, etc.

By organizing a programmatically accessible address space:

¦ Real or physical memory- memory, the addressing method of which corresponds to the physical location of its data;

¦ Virtual memory is memory whose addressing method does not reflect the physical location of its data;

¦ Overlay memory is memory in which there are several areas with the same addresses, of which only one is accessible at a time.

By remoteness and accessibility for the central processor:

¦ Primary memory is accessible to the central processor without any access to external devices. These are processor registers (processor or register memory) and processor cache (if any);

¦ Secondary memory is accessible to the central processor by direct addressing through the address bus (addressable memory) or through other pins.

In this way, the main memory (memory intended for storing current data and executable programs) and input/output ports (special addresses through access to which interaction with other equipment is realized);

¦ Tertiary memory is accessible only through non-trivial sequences of actions. This includes all types of external memory accessible through I/O devices.

Computer memory is one of the most important issues in computer design, as it provides support for one of the most important functions of a modern computer - the ability to store information for a long time.

One of the main elements of a computer that allows it to function normally is memory.

All personal computers use three types of memory: RAM, permanent memory and external (various storage devices).

The internal memory of a computer is where the information it works with is stored. External memory (various drives) is designed for long-term storage of information. Computer memory provides support for one of the most important functions of a modern computer - the ability to store information for a long time. Together with the central processor, the storage device is the key link.

Here we will also talk about what BIOS setup programs may look like. For now we will talk about “standard” programs that are built into the BIOS itself. 1.1. The computer boot process So, let's try to understand the essence of the processes that occur when the system starts. These processes, in accordance with all settings, are initiated by BIOS program. Detecting devices Immediately after turning on or restarting the computer, a search is performed for the video adapter installed in the system. This was done for the simple reason that without a video adapter, the computer will not be able to display information on the screen at all, and its further work on presenting the results of self-diagnosis will be completely meaningless. Typically, if the video system cannot be initialized, the computer stops working and produces an error sound. Let's assume that the video adapter is detected. In this case, it is initialized, after which an image appears on the screen, which may contain information about the video adapter installed in the system, the amount of its memory, as well as some other details (for example, the logo of the video adapter manufacturer may be displayed). Determining the video adapter occurs even earlier than determining the type of processor and installed RAM. However, if the processor is not installed at all or cannot be used, then the system will not be able to display an image on the screen or signal with sound. After the video adapter is initialized, the processor type is determined. At this stage, its clock frequency is also set in accordance with the BIOS settings. Information about the type of processor is displayed on the screen, for example, like this: Pentium IV at 2600 MHz. The boot program then determines the type and amount of RAM installed in the system. After this, memory testing occurs. Information about the results of these processes is also displayed on the screen. Then initialization and verification of devices connected to the IDE controllers begins. These can be hard drives, CD or DVD drives, and other storage devices. Information about these drives is usually taken from the BIOS settings. If auto-detection of drives is specified in the settings (Auto value), the system will try to detect them automatically - however, this will require a little more time. After the described steps, the computer boot program checks the floppy drive, if installed. To do this, the controller sends several commands to the disk drive, and the system waits for its response. Then the search begins and checks the expansion cards connected to the system, which can be located either in PCI slots, and in bus connectors of other types - ISA, AMR, CNR, etc. Such a board can be an internal modem, sound card, video capture card, TV tuner or FM tuner card, etc. Some of these boards ( for example, a SCSI controller) may have its own BIOS. In this case, control can be transferred to her for a while.

For each external device in the computer there is an electronic circuit ( controller or adapter ), which controls it. Some controllers (for example, a disk controller) can control multiple devices at once.

2) All controllers and adapters interact with the processor and RAM via system backbone data transmission called a bus. Tire – a system board that provides input-output information. The characteristic of the bus is the exchange speed.

Main bus types (arranged in order of performance improvement): ISA, EISA, VESA, PCI, AGP. Connectors are “slots” of the PCI standard. It was born about 10 years ago and today is the main standard for connection slots additional devices. PCI slots are usually the shortest ones white, divided by a kind of “jumper” into two unequal parts. Previously, a video card was also installed in the PCI slot; now the AGP (Advanced Graphic Port) connector is used for this purpose. This is a special slot that is faster in terms of throughput. The remaining slots are not installed in new computers.

To simplify the connection of devices, the electronic circuits consist of several modules - electronic boards. On the main board of the computer - systemic (maternal) – the processor, coprocessor, RAM and bus are located. Circuits that control external computer devices (controllers or adapters) are located on separate boards inserted into standardized connectors (slots) on the motherboard. “Socket” for installing a processor: each processor form factor has its own type of motherboard, which is usually incompatible with other processors. So it is impossible to install a PentiumIII processor in the socket AMD processor K7. And vice versa.

So, today there are three motherboards on the market, for installation of three different classes processors:

boards with Slot 1 connector are designed for processors from Intel. Connector type – slot (long slot-like socket).

boards with Socket-370 connector are designed to install new Celeron processors from Intel (frequency from 400 MHz). Connector type: square socket.

boards with a Super Socket 7 (Socket A) connector are designed for “alternative” processors from AMD, Cyrix, IBM and others. Connector type: square socket.

One of the controllers that is present in all computers is port controller I/O

Port types:

parallel (LPT1-LPT4), printers and scanners are usually connected to them;

serial asynchronous ports (COM1-COM4), a mouse, modem, etc. are connected to them;

game port – for connecting a joystick;

USB port (USB 2) - a recent development - a port with the highest I/O speed, new models of printers, scanners, modems, monitors, etc. are connected to it...

Device port - chip or reserved area of RAM addresses:
- containing one or more input/output registers; And
- allowing you to connect peripherals computer to external processor buses.

©2015-2019 site
All rights belong to their authors. This site does not claim authorship, but provides free use.
Page creation date: 2016-07-22

Types of computer memory is exactly the question that novice users often put off studying “for later.” But in vain. This greatly interferes with the correct understanding of the functioning of the system as a whole, which means it will be more difficult for you to find mutual language with your “iron friend”. I am sure that studying the software part of your computer must begin with at least a superficial look into the metal jungle. Therefore, today we will talk about memory in general: what it is like, how it is classified and how it differs from itself.

Let's start with the most obvious. We, people, that is, also have our own memory, and it is also not the same. It is clear that it can be visual, tactile, auditory, etc., but now we are not talking about that. From the point of view of functioning mechanisms, memory can be operational and long-term. The computer is about the same.

Human RAM is activated in situations where you need to remember information for a short time, for example, to do something and immediately forget it. Such information is stored in our heads from 5 hours to three months. In hardware everything is very similar. Computer random access memory is called RAM (Random Access Memory) and exists to store information that the processor and currently running programs may need. Information can be stored in such memory until the computer is restarted or until a specific program is terminated.

Permanent memory is “remembered for life.” Of course, you can forget everything by accident, but computer hard the disk may break. Permanent memory stores information that can be useful at any time over long periods of time or throughout life. The computer analogue of such memory is a hard drive. It is always much larger than the RAM capacity, and always slower than the latter. But on it you can store enormous amounts of information, practically without taking up useful space in the apartment. It’s somehow even strange to compare, for example, a bookcase with an ordinary flash drive.

In addition to the distribution into permanent and RAM, computer memory can also be divided into internal and external. Everything is simple here: everything that is inside system unit– internal memory, everything else that we buy separately, carry with us and connect to different systems (flash drives, CD/DVD drives, memory cards, etc.) – external memory. About it we'll talk a little later, and today we are interested in what kind of internal computer memory there is, and everything that can be connected with it.

ROM– Read Only Memory

Its contents are called BIOS. But BIOS is closer to software, now we are talking a little about that. This is your computer's most permanent memory. It is not noticeable externally, but is extremely important for your system. It is she who tests the readiness of all your equipment from the mouse to the processor before loading the OS, starts your system, and then transfers Windows management. There is also a program for controlling the operation of the processor itself and also a number of instructions that His Majesty the CPU can directly access, bypassing other bureaucratic authorities. The contents of this memory are naturally retained when the computer is turned off and cannot be erased or deleted in the normal manner. This will require flashing, special software and a little courage if you decide to do this for the first time. More precisely, the ability to edit data in ROM depends on its type.

ROM is a masked ROM. The data in such microcircuits is hardwired during the manufacture of the microcircuit and cannot be changed in any way. The only thing left to do is throw away the failed microcircuit. This is not the best option - users decided and stopped buying such microcircuits.
PROM or PROM (Programmable ROM) - similar to the previous one, except for the production method. In this option, data is recorded programmatically once too. This did not change the essence, so such microcircuits also disappeared into oblivion.
EPROM or EPROM (Erasable ROM) is better. Here you can already erase or write data, but so far only with the help of UV radiation. In this version, the need for specific equipment was very annoying. These microcircuits are also no longer produced.
EEPROM or EEPROM (Electrically erasable PROM or flash chip) - we erase and write data without additional devices and even without removing it from the computer as many times as necessary.

By way of additional information, it may be interesting that in the technical literature you can find the term “embedded software” (Software). This is not entirely true, since firmware is not the chip itself, but rather the software that is stored on it.

CMOS - semi-permanent memory

It is powered by a small battery and has very low power consumption. Some are stored there system settings, for example, date and time, which, as you noticed, do not go astray even after turning off the computer from the network.

Cache memory

This is the memory of myself high level, to some extent it can be considered a type of RAM. It is an additional link or a kind of buffer between slower devices for reading data (for example, RAM or hard drive) and the processor, but it does not increase the address space in any way. It is much faster and more expensive than RAM and is designed to store the most frequently used and necessary information for the processor. This information is selected programmatic method using a special algorithm and is placed in the cache, from where the CPU will take it in the next cycles of its work. First of all, the processor accesses the cache, and only then, if necessary information is missing there, it’s RAM’s turn. Information in the cache can be stored of various types, for example, you can find blocks of regular data from main memory or some other official information like, tablets of the current correspondence of data and addresses where they can be found in main memory. There are three levels of cache.

L1 usually lives on the same die as the CPU. It is designed to store commands and data currently being processed by the processor. It differs in that access to memory cells is carried out at the clock frequency of the processor itself, that is, with almost no delays. Manufacturers are inventing various miracles for the cache - for example, associative memory, which allows you to select data not by its addresses, but by its contents. Almost indexed search in our OS. Of course, this significantly speeds up the system.
L2 or external cache used to be mounted on the motherboard near the CPU. Now built into the processor along with the first level cache. Its memory capacity is much larger.
L3 can occasionally be found on high-performance workstations, servers and other sophisticated equipment.

The characteristics of the cache (if any) are also usually indicated next to the processor. Cache sizes are very small and in the slowest version usually reach several Megabytes at best. In a little more detail, the processor is sometimes forced to make empty cycles to wait for data to arrive from the much slower RAM. It is in this situation that the cache is triggered. Something like this.

Registers

The processor also has some super-mega-hyper-performance memory. Otherwise, it would be difficult for him to remember what he is doing at the moment. Sclerosis, you know, is not a pleasant thing. Seriously, registers most often store data for the arithmetic logic unit ALU. They are controlled directly by the compiler, which sends information to the processor for subsequent processing. Anyone who is not a programmer does not need to remember this.

RAM – Random Access Memory

The same operative. Immediately after turning on the computer, she collects many system files from the hard drive to the processor and programs that the system thinks will be running at the moment. How more programs you have in startup, the more processes start with the system, the more memory they need, and the slower your computer turns on. RAM also stores data that has not yet been saved to permanent memory (hard disk). That's why at the moment emergency shutdown All unsaved information on the computer is lost. The larger the amount of RAM, the more information useful to the processor can be stored in it, and the faster your entire system works. Information in RAM is constantly changing as needed - new information is remembered, old information is written to the hard drive and discarded when necessary. If the RAM becomes full, the computer starts to slow down quite a bit. Increasing the size of the paging file partially helps, but, as a rule, for Windows systems this is not a panacea, especially since this file by default has a dynamic size, that is, an expandable size if necessary. This means that changing its size manually is absolutely pointless. In this file, automatically created by the system on the hard drive or the so-called virtual memory, the most rarely used data is automatically reset from the RAM in order to relieve it a little. It is much easier for the processor to work with RAM than with hard drive. And for permanent storage of information, RAM is not suitable due to its high cost (compare the cost of a 1 GB RAM module with the price of a hard drive with a capacity of, for example, several hundred GB), but the main thing is its volatility. Information in RAM is stored with the direct participation of electricity and is erased within a split second after the power supply to the system is stopped. If you manage to take a dump (a screenshot of its contents) in these fractions of a second, you can quite easily break even the most complex encryption algorithm. This weakness both paid and free information encryption programs. Its important characteristics are the volume and speed of access. It is clear that the more of both, the better. And one important point regarding the volume: a 32-bit system will not see more than 3 GB of RAM installed in it (to be more precise). On 64-bit systems, the sky is the limit.

HDD

This is your system's permanent non-volatile memory. It is on the hard drive that the entire operating system is stored along with user data. It's rare, but it happens that a hard drive fails. In this case, it will be possible to restore the system and all the information that was stored on it only with your prayers. More precisely, restoration may well be possible either partially or completely, but its very possibility depends on what exactly and how it broke in the hard drive. Beginners will likely need help from more experienced users. A reminder to regularly backup important information for you.

It is clear that hard drives are characterized by their capacity, but another important characteristic is the rotation speed. A hard drive is a round magnet that literally sticks information to itself. This information is read by special fixed heads, to which the hard disk, rotating at a certain speed, substitutes its cells with the bits and bytes of data stored there necessary for reading. Of course, the faster the hard drive spins, the faster information is read, the faster files and other useful things are copied and pasted. In a word, this is a useful bonus for the speed of your computer and the comfort of your work. If you take apart the old hard drive, you will see all this equipment with your own eyes. If you take the new one apart, you will also see it, but even prayers will not help to restore the disk itself or the information that was stored there.

Video memory

This is RAM, which is used for multimedia needs, or more precisely, it stores the image currently displayed on the screen of your monitor.

Memory Addressing

In principle - somewhere in the near future this will become a topic for a separate article, but since we are already talking about memory... All memory, no matter what it is, consists of a device on which bits and bytes of information are stored and something that knows how to read it. This is implemented in different ways - information is either magnetized (hard disk) to the surface or stored in dynamic RAM using electricity (no charge - zero, charge - one). You can take a thin plastic plate and burn a specific pattern (DVD) into it with a laser. 100 years ago there were punch cards with holes in certain places... In in this case The storage method is not important, but the point is that any medium is divided into many tiny cells, each of which can store one bit of information (a zero or a one). It is the smallest unit of information that ultimately makes up the movie you watch, the music you listen to, and everything else on your computer. Those, in turn, are grouped into bytes (8 pieces each). For this reason, manufacturers are “joking” and selling you hard drives with a capacity of several tens of GB less than declared. Here you have 1 GB, which contains 1024 bytes, and not 1000, as manufacturers think. And now a little math. Each cell has own number or the address at which it can be accessed by a processor or program that needs what is in this cell. It is precisely 32-bit addressing in systems of the corresponding architecture that makes it impossible to have more than 4 GB of RAM (a little memory is reserved for vital needs). In addition, there is also the processor bit capacity, which determines the amount of data that can be processed simultaneously. A 32-bit processor can simultaneously work with 4 bytes of information (1 byte = 8 bits), and a 64-bit processor can handle 8 bytes at once. Thus, a 32-bit processor with clock frequency 800 MHz will perform 800 million operations per second (the calculation is very approximate), and the memory must keep up with it so that useful time is not wasted. Perhaps we could stop here, but still, in the end, I will remind you of one more classification. Memory can also be divided into types from the point of view of reaction to possible errors. Memory without parity will not check them at all. Parity memory contains 1 parity bit for every 8 bits of data, specifically for such checks. ECC itself can find several erroneous bits, and at the same time correct single-bit errors.

Subscribe to our

Personal computer memory. Memory is designed to store programs and data that the processor directly works with. It consists of cells whose location is determined by a unique address. In addition to temporary data, which is determined by what the computer is doing in currently, he must know and constantly remember some standard programs and data. Solving the problems of storing various types of information and reliable functioning of a personal computer has led to the use of several types of internal and external memory

Internal memory RAM is designed to store information and is implemented using a set of chips installed on the motherboard. Memory modules are plates with rows of contacts on which large integrated memory circuits are placed. Random access memory (RAM) Read-only memory (ROM) Cache memory

The memory of the random access memory device stores temporary information that changes as the microprocessor performs various operations. This kind of memory provides access to any randomly selected memory cell at any time. This property is reflected in the English name of the operational RAM memory(Random Access Memory - random access memory). We must not forget that RAM is a volatile device, i.e. when the computer's power is turned off, all information in the RAM is erased. RAM is characterized by high speed and relatively small volume. For modern computers, the memory capacity range is 16 - 512 MB. RAM

The ROM memory stores information recorded at the manufacturer; it must remain unchanged for a long time. Constant information includes basic system programs that automatically start when you turn on the computer. The computer can read or execute programs from permanent memory, but it cannot change them or add new ones. ROM memory is intended only for reading information. This property of persistent memory explains the often used English name ROM (Read Only Memory). ROM memory is also implemented in the form of integrated circuits. The difference is that these chips are non-volatile. Turning off the power does not result in data loss. There are two main types of microcircuits ROM memory, once programmable (after recording, the contents of the memory cannot be changed) and repeatedly programmable. ROM

Cache memory To increase computer performance and coordinate the operation of devices with different speeds, a modern computer uses another type of memory - cache memory (from the English cache - hiding place, warehouse). Cache memory is an intermediate storage device or buffer. It is used when exchanging data between the microprocessor and RAM, between RAM and an external storage device. Using cache memory reduces the number of accesses to hard drive for read-write, since it stores data, repeated access to which on the part of the processor does not require repeating the reading process or other information processing. There are two types of cache memory: internal (from 8 to 64 KB), located inside the processor, and external (from 256 KB to 1 MB), which is installed on system board. microprocessor RAM External drives

External memory External memory is designed for long-term storage of programs and data. External memory devices (drives) are non-volatile; turning off the power does not lead to data loss. They can be built into the system unit or made in the form of independent units connected to the system unit through its ports. An important characteristic of external memory is its volume. The amount of external memory can be increased by adding new drives. No less important characteristics of external memory are the access time to information and the speed of information exchange. These parameters depend on the device for reading information and the organization of the type of access to it.

NGMD Flexible magnetic disks, or floppy disks, are the most common storage media. The most popular flexible disks are 3.5" (inch), (3-inch). The disks are called flexible because the plastic disk located inside the protective sleeve actually bends. That is why the protective sleeve is made of hard plastic. The disk is covered on top with a special magnetic layer, which provides data storage. Information is recorded on both sides of the disk along tracks that are concentric circles. Each track is divided into sectors. The density of data recording depends on the density of the tracks on the surface, i.e., the number of tracks on the surface of the disk. also on the density of information recording along the track. There are DD, HD and ED standards for 3.5" floppy disks, the volume of recorded information is from 720 KB to 2.88 MB. The most common are 3.5" HD floppy disks. As a storage medium, floppy disks are almost obsolete. themselves, small volume, low read/write speed, and unreliability make their use unprofitable.

HDD Hard magnetic disks, or “hard drives,” are an essential component of a personal computer. There are different versions of the origin of the name "Winchester". According to one of them, the first hard drives were released at an IBM branch in the small town of Winchester. A hard drive is several aluminum plates coated with a magnetic layer, which, together with the reading and writing mechanism, are enclosed in a hermetically sealed case inside the system unit. Hard drives have advantages over floppy drives in two main ways: capacity hard drives significantly higher and ranges from several hundred megabytes to hundreds of gigabytes; the speed of information exchange is 10 times greater. To access the hard drive, use the name specified by the Latin letter C:. If a second hard drive is installed, it is assigned the following letter of the Latin alphabet D: . The computer provides the ability, using a special system program conditionally split one disk into several. Such disks that do not exist as a separate physical device, but represent only part of one physical disk, are called logical disks.

CD-ROM CD-ROM drives. Compact discs, which were used for audio equipment, were modified for use in PCs and have now become an integral part of modern computers. It is an excellent storage medium, more compact, convenient and cheaper than a hard drive. It is designed as an internal device and has a 5.25" drive size. Usually managed via IDE, SCSI interface or sound card. The disc is made of polycarbonate, which is coated on one side with a reflective layer (made of aluminum or gold). Recording is carried out using a laser beam that burns alternating depressions in the surface of the metal layer. The main characteristic is the data transfer speed. The reading unit is the reading speed from a magnetic tape. The reading speed of subsequent devices is a multiple of this and varies from 150 KB. /sec. Up to 6 -7 MB. /sec. The quality of reading is characterized by the error rate and is an estimate of the probability of distortion of an information bit when it is read. This parameter reflects the device's ability to correct read/write errors. Average access time is the time it takes for the drive to find the necessary data on the media. Varies from 400 to 80 ms.

DVD-ROM DVD (Digital Video Disk) - discs that will replace CD-ROM, were originally developed for home video. They differ in that they can store a volume of data many times greater than the capabilities of CDs (from 4.7 to 17 GB). The level of sound and image quality stored on DVD is close to studio quality. DVD drives use a narrower laser beam than CD-ROMs, so the thickness of the disc's protective layer was reduced by half, which led to the appearance of double-layer discs.

Flash memory Flash memory, introduced in the late 1980s (Intel), is a member of a class of electrically erasable programmable read-only memory devices. However, it erases an entire area of cells at once: a block or the entire chip. This provides faster recording of information or, as it is otherwise called this procedure, memory programming. To simplify this procedure, special blocks are included in the chip that make the recording “transparent” (similar to recording in a regular memory) for the hardware and software environment.

Different kinds flash memory Portable DVD-ROM drive; can be used both when connected to a computer as a DVD-ROM, and as a DVD player when connected to a TV. DISK STENO is nothing less than autonomous external USB 2. 0 CDRW drive combined with a 6-format card reader. Can read information from six main types of flash cards, can also be used as an external write drive. ZIP Pro drive. It can perform simple tasks that boil down to transferring small amounts of work data and large amounts of entertainment data, such as music, movies and games.

Nixvue Digital Album Flash Cards Once a memory card (used, for example, in a digital camera) is full, data from that card can be copied to a digital album; It is possible to print photos without a computer. OLYMPUS CAMEDIA MXD 512 P x. D-Picture Card Card memory, designed for long-term (tens of years) data storage in the absence of a power source. Used in digital cameras and other devices. USB Flash Drive Resource - up to 1,000 rewrite cycles. The guaranteed data storage period is up to 10 years. Smart. Media Flash Card A memory card designed for long-term data storage. Used in digital cameras and other devices Compact Flash Card Memory card designed for long-term (tens of years) storage of data in the absence of a source. Used in digital cameras, pocket computers and other devices SD Memory Card Memory card; used in MP3 players, digital cameras, PDAs, smartphones and other devices.

Memory (computer)

RAM module inserted into the motherboard

Computer memory (storage device, Memory device) - part of a computer, a physical device or medium for storing data used in calculations for a certain time. Memory, like the CPU, has been a constant part of the computer since the 1940s.

At the everyday level, the word “memory” has a narrower meaning - semiconductor random access memory (RAM), used as RAM on a personal computer (memory stick or memory module). However, the concept of memory is much broader.

Computer memory has always had a hierarchical structure and involves the use of several storage devices with different characteristics.

The most well-known means of machine data storage used in personal computers are: RAM modules, hard drives (hard drives), floppy disks (floppy magnetic disks), or flash memory.

Memory functions

Computer memory provides support for one of the functions of a modern computer - the ability to store information for a long time. Together with the central processor, the storage device is the key element of the so-called von Neumann architecture, the principle underlying most modern computers. general purpose.

The first computers used storage devices solely to store processed data. Their programs were implemented at the hardware level in the form of strictly defined executable sequences. Any reprogramming required a huge amount of manual work to prepare new documentation, reconnection, restructuring of blocks and devices, etc. The use of von Neumann architecture, which provides for storing computer programs and data in shared memory, radically changed the situation.

To date, many different devices have been created for storing data, many of which are based on the use of a variety of physical effects. There is no universal solution; each contains certain shortcomings. Therefore, computer systems are usually equipped with several types of storage systems, the main properties of which determine their use and purpose.

Physical basis of functioning

Read Only Memory, ROM is a type of storage memory designed to store and read data that never changes. Data is written to ROM during its manufacturing process, so it cannot be changed by the user. The most common ROMs made on integrated circuits(LSI, VLSI) and optical CD-ROMs and DVD-ROM.

Programmable Read Only Memory, PROM is a type of memory in which data can be written or changed by exposing the storage medium to electric, magnetic and/or electromagnetic (including ultraviolet or other) fields, often under control special program. There are write-once EPROMs and erasable EPROMs. EPROM, Erasable PROM ), including:

Electrically programmable ROM (EPROM) Electrically Alterable Read Only Memory, EAROM )
Electrically Erasable Programmable ROM (EEPROM) Electrically Erasable Programmable Read-Only Memory flash memory), different high speed access and the ability to quickly erase data
By energy dependence

Holographic memory(English) holographic storage) - spatial graphic information displayed in the form of interference structures is used as a recording and storage medium.

Matrix memory(English) matrix storage) - a type of memory whose elements (cells) are arranged in such a way that they can be accessed along two or more coordinates.

Multi-block memory(English) multibunk memory) is a type of RAM organized from several independent blocks that allow simultaneous access to them, which increases its throughput. The term “interliving” (tracing paper from English) is often used. interleave- interleave) and can be found in the documentation of some companies “multi-channel memory” (eng. Multichanel).

Multi-input memory(English) multiport storage memory) - a memory device that allows independent access from several directions (inputs), and requests are serviced in order of their priority.

Multi-level memory(English) multilevel memory) - a memory organization consisting of several levels of storage devices with different characteristics and viewed by users as a whole. Multi-level memory is characterized by a page organization, which ensures “transparency” of data exchange between memories of different levels.

Directly managed (RAM) memory(English) on-line storage) - memory directly accessible to the central processor at a given time.

Object-oriented memory(English) object storage) - memory, the management system of which is focused on storing objects. Moreover, each object is characterized by the type and size of the record.

Overlay memory(English) overlayable storage) - a type of memory with overlapping called in different time software modules.

Memory parallel action (English) parallel storage) - a type of memory in which all search areas can be accessed simultaneously.

Reloadable control memory(English) reloadable control storage) - a type of memory designed for storing control microprograms and allowing multiple changes of content - automatically or under the control of the computer operator.

Relocatable memory(English) data-carrier storage) - a type of archival memory in which data is stored on a relocatable medium. There is no direct access to them from the computer.

Sequential memory(English) sequential storage) - a type of memory in which data is written and retrieved sequentially - digit by digit.

CPU memory, processor memory(English) processor storage) - memory, which is part of the processor and is intended for storing data directly involved in the execution of operations implemented by the arithmetic-logical unit and control device.

Memory with built-in logic, functional memory(English) logic-in-memory) - a type of memory containing built-in facilities logical processing(transformation) of data, for example scaling it, converting codes, overlaying fields, etc.

Working (intermediate) memory(English) working (intermediate) storage ):

A part of computer memory intended for storing temporary data sets.

Memory for temporary storage of data.

Real memory(English) real storage) - all physical memory of a computer, including main and external memory, accessible to the central processor and intended for storing programs and data.

Register memory(English) register storage) - a type of memory consisting of general-purpose registers and floating-point registers. As a rule, it is contained entirely within the processor.

Free (available) memory(English) free space) - an area or space of memory that can currently be allocated for loading a program or writing data.

Semantic memory(English) semantic storage) - a type of memory in which data is stored and written off in accordance with a certain structure of conceptual features.

Shared memory(English) shareable storage) - a type of memory that can be used simultaneously by several processors.

Protected memory, protected memory(English) protected storage) - a type of memory that has built-in means of protection against unauthorized access to any of its cells.

Serial access memory(English) sequential access storage) - a type of memory in which the sequence of input messages and data samples addressed to them corresponds to the sequence in which their records are organized. The main method of searching for data in this type of memory is sequential enumeration of records.

Direct access memory, random access memory (RAM)(English) Random Access Memory, RAM) - a type of memory in which the sequence of input messages and data samples addressed to them does not depend on the sequence in which their records are organized or their location.

Word-based memory(English) word-organized memory) - a type of memory in which addressing, recording and retrieving data is carried out not byte by byte, but word by word.

Static memory(English) static storage) - a type of memory in which the position of data and their value do not change during storage and reading. A variation of this type of memory is static RAM.

Page memory(English) page memory) - memory divided into identical areas - pages. Exchange with such memory is carried out by pages.

Control memory(English) control storage) - memory containing control programs or microprograms. Typically implemented in the form of ROM.

Different types of memory have different advantages, which is why most modern computers use multiple types of storage devices.