A lot of computer users often wonder what RAM is. To help our readers understand RAM in detail, we have prepared material in which we will look in detail at where it is can be used and what are his types are now in use. We will also look at a little theory, after which you will understand what modern memory is.

A little theory

The abbreviation RAM stands for - random access memory. Essentially, it is the RAM that is primarily used in your computers. The operating principle of any type of RAM is based on storing information in special electronic cells. Each cell is 1 byte in size, meaning it can store eight bits of information. Each electronic cell has a special address. This address is needed so that you can access a specific electronic cell, read and write its contents.

Also, reading and writing to an electronic cell must be carried out at any time. In the English version, RAM is RAM. If we decipher the abbreviation RAM(Random Access Memory) - random access memory, then it becomes clear why the cell is read and written at any time.

Information is stored and rewritten in electronic cells only when your PC works, after turning it off, all information that is in RAM is erased. The totality of electronic cells in a modern RAM can reach a volume from 1 GB to 32 GB. The types of RAM currently in use are called DRAM And SRAM.

• First, DRAM is dynamic RAM, which consists of capacitors And transistors. The storage of information in DRAM is determined by the presence or absence of charge on the capacitor (1 bit of information), which is formed on the semiconductor crystal. To store information, this type of memory requires regeneration. Therefore this slow and cheap memory.
• Second, SRAM is Static RAM. The principle of cell access in SRAM is based on a static flip-flop, which includes several transistors. SRAM is an expensive memory, so it is used mainly in microcontrollers and integrated circuits, in which the memory capacity is small. This fast memory, not requiring regeneration.

Classification and types of SDRAM in modern computers

The most common type of DRAM memory is synchronous memory SDRAM. The first subtype of SDRAM is DDR SDRAM. DDR SDRAM memory modules appeared in the late 1990s. At that time, computers based on Pentium processes were popular. The image below shows a 512 MB DDR PC-3200 SODIMM stick from GOODRAM.

Console SODIMM means that the memory is intended for laptop. In 2003, DDR SDRAM was replaced by DDR2 SDRAM. This memory was used in modern computers of that time until 2010, until it was replaced by the next generation of memory. The image below shows a 2 GB DDR2 PC2-6400 stick from GOODRAM. Each generation of memory demonstrates increasingly faster data exchange speeds.

The DDR2 SDRAM format was replaced in 2007 by an even faster DDR3 SDRAM. This format remains the most popular to this day, although a new format is breathing in its back. The DDR3 SDRAM format is now used not only in modern computers, but also in smartphones, Tablet PCs And budget video cards. DDR3 SDRAM is also used in game consoles Xbox One eighth generation from Microsoft. This set-top box uses 8 gigabytes of DDR3 SDRAM format RAM. The image below shows a 4 GB DDR3 PC3-10600 memory from GOODRAM.

You can install the above modules from any manufacturer, but these RAM modules are best suited. They are presented on the official page for the motherboard in the paragraph “ Memory Support List", since their compatibility has been verified by the manufacturer.

The example shows how easily you can find out information about the system unit in question. In the same way, RAM is selected for all other computer configurations. I would also like to note that using the configuration discussed above, you can run all the latest games with the highest graphics settings.

For example, on this configuration new games such as Tom Clancy's The Division, Far Cry Primal, Fallout 4 and many others, since such a system meets all the realities of the gaming market. The only limitation for this configuration is that it price. The approximate price of such a system unit without a monitor, including two memory modules, a case and the components described above, will be about 2000 dollars.

Classification and types of SDRAM in video cards

New video cards and older models use the same type of synchronous SDRAM memory. In new and outdated video card models, this type of video memory is most often used:

• GDDR2 SDRAM - bandwidth up to 9.6 GB/s;
• GDDR3 SDRAM - bandwidth up to 156.6 GB/s;
• GDDR5 SDRAM - bandwidth up to 370 GB/s.

To find out the type of your video card, the amount of RAM and memory type, you need to use a free utility GPU-Z. For example, the image below shows the program window GPU-Z, which describes the characteristics of the video card GeForce GTX 980 Ti.

GDDR5 SDRAM, which is popular today, will be replaced in the near future by GDDR5X SDRAM. This new classification of video memory promises to raise throughput before 512 GB/s. The answer to the question of what manufacturers want to achieve from such a large throughput is quite simple. With the advent of formats such as 4K and 8K, as well as VR devices, the performance of current video cards is no longer sufficient.

Difference between RAM and ROM

ROM stands for read only memory. Unlike random access memory,ROM is used to record information that will be stored there permanently. For example, ROM is used in the following devices:

• Cell phones;
• Smartphones;
• Microcontrollers;
• BIOS ROM;
• Various consumer electronic devices.

In all the devices described above, the code for their operation is stored in ROM. ROM is non-volatile memory, therefore, after turning off these devices, all information will be stored in it - which means this is the main difference between ROM and RAM.

Let's sum it up

In this article, we briefly learned all the details, both in theory and in practice, regarding random access memory and their classifications, and also looked at the difference between RAM and ROM.

Also, our material will be especially useful to those PC users who want to find out their type of RAM installed in the computer, or find out which RAM must be applied to different configurations.

We hope our material will be interesting for our readers and will allow them to solve many problems related to RAM.

Video on the topic

What is it and what features does it have? And what types of this RAM are there? I will try to answer these and many other questions in this article.

The programs we run run in RAM, the processor resets the processed data, which is first copied to RAM and then saved to the hard drive.

The peculiarity of RAM is that:

1. It has fast speed of reading and writing data.
2. The information in it is stored only as long as voltage is applied to the memory modules

That is, if you worked in any program: Word, Excel, photo editor, without saving this data and at that moment turned off the light, then you can say goodbye to this data or the changes made.

Types of RAM

Today there are three main types of memory for PCs:

1. DDR (400 MHz)
2. DDR 2(533 MHz ,667 MHz, 800 MHz ,1066 MHz)
3. DDR 3(1333 MHz ,1600MHz, 1800MHz,2000MHz ,2133MHz, 2200MHz, 2400MHz, 2600MHz, 2800MHz, 3000MHz)
4. In 2014, DDR 4 appeared (2133MHz, 2400MHz and higher)

DDR is the oldest and slowest RAM you can still find on sale. Computers were assembled on its basis from 2003 to 2006.

DDR 2 is faster memory. It is 2 times faster than DDR. On its basis they collected system units from the end of 2006 to 2011. But now it’s better to stop at DDR 3 - since one 2 GB DDR 2 stick costs exactly 2 times more than a DDR 3 stick of the same volume.

DDR 3 RAM was released in 2007. The performance increase relative to DDR 2 (800 MHz) was about 5-7%, not so much, but still nice!

- SRAM(Static RAM - static RAM) - has fast access to information and does not require regeneration, but is somewhat more expensive than DRAM. Mainly used for cache and registers.

- DRAM(Dynamic RAM - dynamic RAM) - requires regeneration, and therefore access time is longer than the previous type. Almost all modern RAM modules for personal computers have this standard.

The figure above shows a DRAM memory element. In fact, it is a microcircuit, several of these microcircuits are installed on a wafer.

-SD RAM(Synchronous Dynamic RAM - synchronous dynamic RAM) is a subclass of DRAM memory, which has the peculiarity that it uses synchronous data exchange. That is, it allows you to receive commands regardless of whether the previous command was executed or not.

Due to the fact that dynamic memory cheaper, then it is precisely this that is used for RAM. It is made of tiny capacitors and transistors to control the charging process. Physically, the memory is made of semiconductor material with the formation of elementary cells in which row information from 1 to 4 bits is stored. The rows are combined into matrices called a page, which in turn create an array called a bank. When reading the information, the capacitors are discharged and it is determined whether there was a charge in it or not. If a charge is present, the capacitor is recharged. Over time, the charge drains, and the stable storage time is measured in milliseconds. In static memory, two transistors are used per bit of memory, one is on, the other is off, they correspond to two memory states. Dynamic memory, on the other hand, uses one transistor per bit, so it packs more memory into the same area, but it will run slightly slower. Therefore, static memory is used for cache memory.

To save information, a rewrite operation is used, which is called memory regeneration, at which the capacitors are recharged. However, the CPU has access to data in a refresh-free cycle. To coordinate between RAM and processor clock speed, there is a parameter - the wait state (Waitstate), indicating the number of clock cycles that the processor should skip between two accesses to the system bus. The greater the number of cycles in this parameter, the slower the computer runs. To set this parameter, use the Setup program.

DRAM was used mainly in the 80286 computer and partially in the 386SX. Currently, they are used as composite memory modules SIMM, DIMM, which will be discussed below.

Memory modules may differ from each other by type of architecture (Std or FPM, EDO, BEDO and SDRAM), by type of location (DIP, SIMM, DIMM and others), by error control method. There may be other differences, for example, different voltage ratings, regeneration parameters, etc.

Error Control Methods. Memory modules are divided into the following types:

Without parity, that is, without error checking. This type is the most common, since the memory works quite reliably;

With parity, that is, an odd parity check, and when errors occur, a signal is sent to the central processor about their presence;

ECC – control with a code that allows you to restore data in case of an error;

EOS – control with a code for restoring information in the event of an error and checking for odd parity;

Modules that artificially produce an odd bit by recalculating it, that is, with virtually no parity. Allows you to work on those boards that require parity.

Parity check means the following. Each byte, as we know, contains eight bits. Some types of memory contain, instead of eight, nine bytes, the ninth for parity checking, that is, the sum of the first eight bytes modulo 2 is taken and this value is placed in the ninth bit. When reading data, if the sum does not match the value in the ninth bit, an error is generated, which is called a parity error. The odd parity check is carried out similarly, when the value opposite to the sum of the first eight bits is entered into the ninth bit. For example, if there is a value in the first eight bits of “00100100”, then the sum is 10V in binary. The value modulo two is zero. When checking for odd parity, the ninth bit will contain the value “1” (the opposite of zero). To check for odd parity, the value will be “001001001”. Odd parity checking is used more often, since the zeroing of a memory section is detected by this particular check (in this case, the sum of zeros will be even and equal to zero for all nine bits). You can use parity-checked memory on systems that don't require parity, but not vice versa.

Thus, if there are 9 chips, then one board with chips is used to check parity, 8 - without checking, that is, the number of chips will be a multiple of 9 or 8 memory bits. Recently, given the reliability of manufactured microcircuits, the parity bit is not used (for example, for 16 MB circuits, one failure for 2-3 years of continuous operation). Parity-checked memory is used in systems where reliability is very critical, that is, in servers that are also constantly loaded. In some cases, when motherboard requires the presence of a parity bit, you can use RAM chips that emulate a parity bit, that is, they actually do not have a ninth bit and do not perform a parity check.

There is a memory called ECC, which is rarely used, but allows you to correct errors when they occur, that is, when errors occur, it analyzes and can restore the damaged bit.

Reliability increases with greater integration. It is higher due to the fact that it has fewer connections, so it is better to buy one 512 MB chip than four 128 MB chips. In this case, you can not use all RAM slots, but only some, which allows you to expand the memory in the future.

Memory interleaving organized in such a way that when regeneration is performed in one bank (it cannot be worked with), the other bank allows read/write operations. In this case, adjacent data blocks are located in different banks. Due to the frequent reading of sequential data, different banks are used for multiple read/write operations.

Memory paging. Addressing is organized like a table, where each element of the table corresponds to a memory element in the computer, that is, to access it, you first need to specify the row number, then the column number. In the case when the next data is nearby, the row addresses can coincide, so when an operation with an adjacent cell is performed, only the column address is indicated, which improves memory performance.

Shared memory. Memory that can be accessed by different devices. For example, the shared memory of the adapter allows it to be accessed both from outside system bus, and from the adapter side.

Shadow Memory. Due to the fact that the data that is in the BIOS is read rather slowly, and may be required frequently, it is copied to the RAM area and then, when the operating system is running, read from there, and not from the BIOS. Shadow memory can be implemented using both software and hardware methods.

Non-standard memory. The computer may contain non-standard memory, which is often the case in laptop computers. As a rule, there are many types of them, but you need to purchase memory only from the manufacturer whose modules are used in the computer. Buying from other manufacturers is often cheaper, but they may not be suitable due to special requirements. Memory for laptop computers is slightly more expensive than for desktop computers. Modern laptop models are switching to the types of memory that are used in desktop computers.

In different types laptops To install RAM, there are holes in different parts of the case, so you need to have the appropriate instructions for them. In more modern laptops, memory is becoming standardized.

Architecture type

The very first was architecture FPM DRAM(Fast Page Mode DRAM - fast with the page method), which has two types of memory with different access times: 60 and 70 nsec; microcircuits with 60 nsec access operate at system bus frequencies of 60, 66 MHz. FPM is also called standard memory and operates in a 5-3-3-3 cycle read burst mode.

The next memory modification is EDO DRAM(Extended Data Output DRAM - extended data output DRAM). Performance is achieved through additional registers that store data during the next request to the chip and allow the next cycle to begin before the previous one ends. Runs 10-15% faster than FPM DRAM. It has access times of 50 nsec, 60 nsec (for a 66 MHz bus) and 70 nsec. Used on motherboards with bus frequencies up to 66 MHz and Pentium processors, less often with a 486 processor. Due to the fact that it operates unstable at a system bus frequency of more than 66 MHz, it gradually left the market.

EDO provides pipelining for memory operation. It is used in SIMM-72 and DIMM boards, and they do not use odd parity, but can store ECC checksums. This type of memory can be used in both RAM and video memory. This type requires the BIOS to be able to handle them, so older motherboards may not support them. Some boards determine the type of memory module using the appropriate BIOS and allow simultaneous installation of standard and EDO memory. Achieves a cycle of 5-2-2-2 in batch reading mode.

BEDO(Burst EDO - packet EDO) - allows you to read data in blocks or packets in one clock cycle. It evolved from SDRAM and operates at a system bus frequency of 66 MHz. At BEDO, the principles of pipeline processing have been further developed. This memory requires slightly more time to fetch the first data in batch mode, but provides faster fetch of the next data. It is also used in SIMM-72 and DIMM boards. Reaches 5-1-1-1 cycle in batch reading mode.

SDRAM(Synchronous DRAM - synchronous DRAM) - provides pipelined data processing and address interleaving, which increases its performance. All operations in such microcircuits are synchronized with the CPU clock frequency and operate at system bus clock frequencies of up to 133 MHz, with a duty cycle time of 8-10 ns at a system bus frequency of 100 MHz. For modern buses, there is memory PC100, PC133, where the numbers indicate the frequency of the system bus. It works faster than EDO DRAM, but at bus frequencies up to 66 MHz the difference in performance is not significant.

SDRAM memory is the most promising, especially for high clock frequencies of the computer system bus, which cannot be effectively supported by other types of memory. This memory is installed on DIMM boards or as a chip on the system or video board. Reaches 5-1-1-1 cycle in batch reading mode.

SDRAM II(DDR SDRAM) allows access commands to be processed in parallel in their independent memory banks, which speeds up access time. This memory accelerates operation by using the leading edge and decay of the pulse by half, and is designated PC1600, PC2100, where the numbers indicate the number of MB/sec that can be transferred over the bus, respectively 1,600 MB/sec using a 100 MHz system bus, and 2100 - for 133 MHz. However, they must be supported by the chipset; you can consult the motherboard manual for this. More details about DDR, DDR2, DDR3 memory are described above.

Memory Direct RDRAM is a promising memory that Intel has switched to. It can operate with a bus clock frequency of 400 MHz/sec, with a throughput of up to 1,600 MHz/sec, allowing data to be transferred on the leading and falling edges of a pulse, and provides pipelined data sampling. In addition to those mentioned, there is SLDRAM memory, which, like Direct RDRAM, at a frequency of 400 MHz allows data transfer of up to 1,600 bytes/sec.

There are modifications of the above types of memory, for example, CDRAM (Cache RAM), EDRAM (Enhanced RAM) - is a DRAM memory that contains static memory, used as a buffer memory in the module. Data access time in the above types of memory ranges from 50 to 70 ns.

In addition, there are other types of memory that are installed on graphics (video) cards (but not for RAM) - VRAM , SGRAM , GDDR 2, GDDR 3, GDDR 4, GDDR 5 . Where GDDR 2 is built on DDR 2, GDDR 3, GDDR 4, GDDR 5 are built on DDR 3.

Modern computers use DDR, DDR 2 and DDR 3.

Types of cases, plates. Memory installation

Placement of modules. Older computers may have used add-on cards to increase RAM up to 32 megabytes. Such memory was installed not using DIMMs and SIMM modules, but using a special card, similar to a sound video card. However, these cards are no longer produced at this time.

In order to avoid difficulties with installing and using microcircuits, the memory is placed on one plate, which is inserted into a special socket on the motherboard. In older computer models, the DRAM module may be manufactured in a dual-in-line package. When installing and removing these elements, you must be careful to ensure that the legs do not bend. To straighten the legs, use thin pliers.

DIP(Dual In-line Package - a case with double-sided outputs) - also an old type of memory, with a capacity of up to 1 megabit, located on the motherboard for models 8086, 286, 386, as well as on graphics adapters. Now they are practically not used for RAM. Their appearance is shown in the figure below. The following types of memory are produced in the form of plates on which memory chips are located.

Modern microcircuits are produced with housings: DIP, ZIP with a zigzag arrangement of contacts, sometimes produced for video memory, SQJ is used in SIMM cards or for special connectors on a video card, TSOP - for installing DIMMs on the board.

Modules SIPP(Single Inline Pin Package - a package with one row of wire leads), or SIP (obsolete). To reduce the space occupied on the motherboard, DRAM modules are located on a wafer that has 30 pins. The appearance of this board is shown in the figure. Before SIPP, SIP modules were used, but they were hopelessly outdated.

The picture above shows a SIPP card and the picture below shows a SIMM card.

Modules SIMM(Single Inline Memory Modules - memory modules in one row), colloquially called “sims” with the emphasis on the last syllable. The SIMM board differs from the SIPP module in that it has a different type of contacts located on the plate, as can be seen in the figure. These modules are equipped with memory chips with 8, 16, 32 or more MB of memory.

All microcircuits that are located on SIMM, DIMM boards are soldered to the board, and it is almost impossible to replace them, so if one module malfunctions, the entire board must be replaced.

For 30-pin SIMMs, you need to use 4 modules for a 486 processor, since one module is 8 bits wide (8 x 4 = 32), and for Pentium - 8 to provide 64-bit. 72-pin SIMM modules have a width of 32, so for 486 processors you need to install one board, for Pentium - two. Pentium DIMMs are installed one per motherboard.

Previously, plates with 30 pins were used. Currently, memory modules have 72 pins. The connector where the memory plates are inserted is shown in the figure below.

To remove it, you need to bend the two clamps at the edges of the board and tilt the board, then remove it. The arrows show where to click. Insertion is done in reverse order. The board is brought at an angle and moved to a vertical position. The clips on the edges themselves are installed in place, as shown in the figure below.

If you are planning to buy a computer and system board There are four memory slots; it is advisable to choose a computer where not all slots are filled, so that other modules can be added in the future. The best way to check the performance of the memory is to install it in the computer and run a diagnostic program.

At first, such modules used the SIMM standard, then DIMM modules appeared. The SIMM module can read one byte at a time. When installing multiple SIMMs, it was often necessary that they have the same characteristics, obey the same signals, and have the same sampling rate. Often chips with modules from different companies or different types one company were not compatible with others.

Modules can be single-sided or double-sided, with single-sided modules usually having microcircuits on one side of the board, while double-sided modules, which contain two banks, have modules located on both sides.

For a motherboard with a Pentium processor, memory banks are used that work with SIMM and DIMM modules.

DIMM(Dual In-Line Memory Module - memory packaged in two rows on the case) has 168, 184, 200 or 240 contacts and a shorter access time than on SIMM boards. In addition, the boards overcome the RAM size limitation of 128 megabytes. Now it can reach a significant value, which is indicated in the documentation for the board. The boards contain 2 rows of 92 or 120 contacts (184 or 240 in total, in older computers - 168). Due to the larger number of contacts, the number of banks in the module increases. The DIMM module already has 32 or 64 lines for reading data (4 or 8 bytes, respectively) and it is now possible to install them in different computers. Additionally, DIMMs have more ground planes. The board may contain non-volatile memory, which contains the parameters of the microcircuits. If the required type of chip is missing, the board will not be able to work with such memory. Unlike SIMM cards, DIMM cards are inserted vertically. Installation of cards of this type of memory is shown in the computer connection section.

SO DIMM(Small Outline DIMM - small-sized DIMM) - boards that have 72, 144, 168 or 200 pins and are used for laptops. This memory has 16 independent memory channels and allows you to work with different devices and programs that access different memory areas simultaneously.

There is also a type - DDR 2 FB - DIMM, used in servers, RIMM has 168, 184 or 242 contacts and a metal shield to protect the contacts from interference (used for RIMM memory, which is almost out of production), MicroDIMM with 60 pins for subnotebooks and laptops.

In addition, there is low profile(Low profile) memory that has a reduced board height for installation in low-profile cases. Note also that some boards operating at higher frequencies may have a radiator in the form of plates.

Installing memory. To install SIMM memory modules, you must first remove the cover of the system unit, remove the old modules (if necessary) and install the boards as described above. Older boards may require jumpers to be installed when adding memory. Next, you need to close the lid of the system unit. When working, remember about electrostatic electricity; when transporting modules from the store, they should be in antistatic bags; when installing microcircuits, you should not touch the contacts with your fingers, as there is grease on your fingers, which can cause poor contact. When installing modules, do not press them hard, otherwise you may damage the motherboard. If installation is inconvenient, it is better to remove the motherboard. If the module does not install, it may be inserted the wrong way, in which case try turning the module over. SIMM cards are inserted obliquely, while DIMM cards are inserted vertically.

Then you need to check whether the system has detected the presence of memory, the size of which can be found in the BIOS program. You can also run a test program to check the installed memory, whether there are any defects in any chip.

Notes. Memory chips are significantly smaller than the case in which they are located, however, in order to make them convenient to mount and to maintain temperature conditions, this particular design is used.

A memory expansion card was used for the 286 because the motherboard did not have a dedicated memory slot. This card connected to the system bus and required a special driver with a specific standard called Lim (Lotus, Intel, Microsoft).

The first standard boards for new Pentium processors had, as a rule, two types of RAM connectors: SIMM and DIMM, each of which is called a bank, and their numbering starts from zero (Bank0, Bank1, and so on), but many boards do not allow the use both of these types of memory are on board. Banks are filled sequentially, that is, first you need to set Bank0, then Bank1. Therefore, it is not possible to set only one Bank1. You can try to determine which memory is on the platter: with parity or not. If there are 8 chips on the plate, then it is without control, if there are nine, then it is with control. It is clear that this is due to the presence of the ninth bit in the byte, which is used to check parity. Currently, boards for Pentium processors are only available with DIMM sockets.

There was a special converter board that was inserted into the SIMM connector, and memory modules into it, that is, if all SIMM connectors are occupied, then they can be installed on the converter and get free connectors where you can add additional RAM.

The numbers of RAM banks are sometimes marked on the motherboard.

If the RAM malfunctions, you should wipe the contacts with an eraser and insert it again, then replace the boards with each other. If the memory worked, then the cause could be a bad contact, since the graphics card consumes a lot of power and gets quite hot. Therefore, during installation, you need to place it in such a way that there is free space between it and other boards, preferably near the fan. In this case, you need to make sure that the fan blades do not touch the wires, otherwise it will fail.

Marking. On boards you may find the marking 1/ /9/ /70, which means 1 - with parity check (9 - number of chips), 70 - access time in nanoseconds. The smaller it is, the better, but it must be supported by all devices, first of all motherboard.

The last digit often determines the access time in nanoseconds, which can determine either the value itself or ten times less. For example, an access time of 70 nanoseconds might be labeled 70 or simply -7. Values ​​for SDRAM can be -10 (meaning 50 ns), -12 (60 ns) and -15 (70 ns).

In new microcircuits, the name of the manufacturing company is first indicated using several characters, for example, M (OKI company), TMM (Motorola), MT - Micron, GM - LG, etc. Each company has a code - a type of cipher, which can be found out via the Internet by visiting the manufacturer's page.

Cache memory

RAM is not all the memory that is in the computer. In addition to it, there is cache memory, which is a buffer between the central processor and RAM, which has already been mentioned. The CPU also has a special cache memory to convert a linear address to a physical address so that it is not recalculated. There is cache memory for working with various devices (for example, a hard drive), which allows you to speed up I/O operations, a keyboard buffer, etc. All these types of memory are invisible and often unknown even to the programmer, since they are implemented in hardware .

This chapter will look at cache memory, which works with the processor and is located between the central processor and RAM. Using cache memory can significantly increase computer performance by reducing processor idle time. This is achieved due to the fact that data transfer from or to the cache is faster than to RAM. If the processor needs to write data to RAM, it writes to cache memory instead, while the processor continues to operate. Further, regardless of the operation of the processor, when the system bus is freed, data will be transferred to RAM using the cache controller. In this case, it is possible not only to write, but also to read data from the cache memory.

The operation of cache memory is effective due to the fact that programs, as a rule, process the same data. In addition, program instructions are arranged one after another or inside a loop, which increases the likelihood of data being present in the cache. If the required data to be read is in the cache memory, then it is said to be a hit; if the required data is not in it, then it must be read from RAM and is said to be a miss. In general, the essence of cache memory is to save an image of areas from RAM, which works faster.

Principles of cache memory organization. Direct Mapped Cache (Direct-mapped cache) partial or set-associative cache). How does he work? The address of the data to be read is divided into three parts. The first one is called tag, the second defines a row, the third a column. The cache is organized in the form of a table of lines of a certain length, for example, 1+16=17 bytes, where the first cell contains the tag value, and then there are 16 data values. Having received an address (for example, 123003Ah), it is divided into three parts: tag (123h), line number (003h) and column number (Ah). IN in this example A conditional division is given, since the dimension of the numbers may be different. The line number is determined by the number, in our example it is 4 (003h, where – 000h is the first line, 001h is the second, 002h– third, 003h - fourth, etc.). At the beginning of the line there is a tag value that is compared with the tag of the received address (123h). If they correspond, the data is sampled or recorded from the corresponding position (Ah – eleventh value, also 0h– for the first, 1h – for the second, ... Ah – for the eleventh); if they do not match, then the required data is not in the cache memory and it is selected from RAM. This type of cache memory is used in 386 processors.

Fully associative the architecture can store the data line anywhere in the cache. The address at which the data is read is divided into two parts: the tag and the number in the line. When a read or write is required, the tags in the entire cache are checked and this one is selected if there is a match. This method requires more steps to find a given one, since you need to look through the values ​​of all tags in memory, that is, more hardware costs.

Dial-associative The architecture uses a combination of the above methods and is the most common. In this case, several rows are combined into so-called sets. The address is divided into three parts, the third, as before, determines the number of the data in the line, the middle one is the set number, and the first part is the tag. Using the middle part of the address, a set is determined where a line is searched that has a tag number at the beginning that matches the first part of the given address. If it is available, then the data is sent from the cache memory to the central processor; if not, then the operation is performed with RAM.

Many routines use a cache for data and a separate cache for CPU instructions. This method is called Harvard. If there is no such division, then the method is called Princeton.

In addition to the above methods, cache memory can be organized in various ways.

At write-through (Write Through) after memorizing the cache memory, writing to RAM is performed. This is the simplest method in terms of implementation, but not the fastest, since after writing to the cache memory, the processor can continue working, and if it needs the bus to receive or write data, it will be busy for writing to RAM, and as a result will be idle CPU. This method was used by the first processors with cache memory (486), but there is a transition to other methods.

Method write-through buffering(Buffered write through) is an improvement on the previous method. With it, the CPU writes multiple data into a buffer and can continue to work while the data is written to the cache memory, and this data will then be transferred to RAM independently of the CPU using a write-through method.

Method write back (Write Back) allows you to not write data to RAM after writing to cache memory. It will be written to after the entire row is written during a row update. This method is faster and requires more hardware. Recently, there has been a transition to this method in modern processors.

In computer literature, sometimes different meanings are attached to cache names L1, L2. Sometimes L1 refers to the cache memory located in the processor, sometimes in the cartridge. We will accept the following designation: L1 is the cache memory, which is located in the processor, L2 is in the cartridge, L3 is on the motherboard. In practice, different manufacturers of central processors may have a different name, for example, Intel and AMD.

First level cache. The cache memory is located inside the processor and therefore is accessed at a higher speed than via the system bus. The cache memory in the first models contained data and instructions in one area. Then it began to be divided into two parts, one of which stores machine instructions, the other - the data itself, which increased the efficiency of the computer. Some processors have introduced a third area - an associative translation buffer for translating virtual addresses into physical ones. The first level cache runs at processor speed. Its volume is small, up to 128 KB.

Second level cache. Older processors have cache memory built into a special cartridge that also houses the processor. This memory is connected to the processor by a separate bus, which has a higher clock speed than the system bus, which allows you to use the computer more efficiently. Modern second-level cache memory is also located on the processor core, synchronizes between processor cores, and is practically located between the first-level cache and the third-level cache.

Third level cache. In 486 computers, this type of memory began to be built into the motherboard. This memory was called L2 cache at the time. Due to the fact that this cache no longer operates at the internal frequency of the central processor, but at the external one, the data transfer rate to this cache memory is lower than to the first level cache. This happens because the internal frequency is higher than the external one. Since RAM and third-level cache operate at the same frequency, and reading/writing occurs to the cache memory in one clock cycle (in older computers - 2 or more), it also has advantages over RAM and increases computer performance . Then the third level cache became known as the cache located on the processor chip (Pentium IV, reaching 4 MB, in modern ones up to 24 MB).

May be used on some computers fourth level cache(usually for servers).

The next level cache is usually larger in size than the previous level cache and its frequency is slower than that of the previous level cache.

Problems when working with cache memory. When working with cache memory, erroneous situations may arise when the cache memory has not yet written data to RAM, and another device (for example, through a DMA channel) tries to read data from memory at the same address, but receives old data. To prevent this from happening, the controller is equipped with a special subsystem that determines who accesses the RAM. In addition, it is possible that the cache memory contains values ​​from ROM memory (read-only). This is implemented so that data stored in ROM memory can be read faster, since they are usually more often in demand. However, you cannot use the cache memory to write to ROM, as this may lead to errors.

The second erroneous case when working with cache memory is possible when data is read from RAM, and at the same time new data is written there through the DMA channel. The same problems can arise when using multiprocessor systems, in which each processor uses its own cache memory. To avoid such cases, all these options must be monitored by the cache memory controller, which must determine what and in what sequence should be written to the RAM and cache memory. However, he does not always cope with these tasks.

Some problems are resolved by specifying in the BIOS those areas of memory in which buffering for cache memory can be carried out, and in which - it is not. If there are frequent cache memory errors, you can disable it using the corresponding option in the BIOS.

Cache memory uses static rather than dynamic memory modules. Several DIP elements are installed on the motherboard. Cache memory consists of three parts: controller, data memory, and instruction memory. The first processors with cache memory had a controller and one memory area for both data and instructions, but later they began to be separated. Typically, the cache memory located in the processor operates at the same clock speed as the processor, on the cartridge it is approximately half the frequency, and on the motherboard it is at the system bus frequency. In modern computers, cache memory is not installed on the motherboard.

Performance. Disabling the L1 cache can sometimes reduce system performance by several times for some types of programs. As a rule, the operating speed of these microcircuits is 20, 15, 12 ns or less, which allows you to perform a 2-1-1-1 burst cycle at a frequency of 33 MHz. Using a Level 2 cache increases system performance by 10-20% (sometimes stated as 20-30%), depending on the type of programs being used. In practice, performance growth stops after 1 MB; 512 KB is optimal (for Level 2 cache).

Some books discuss another level of cache memory, which is actually defined as the size of a buffer located in RAM and used to improve performance with some peripheral devices ( HDD, optical drives and others).

Access time should not be large, so statistical memory (SRAM) is used. After installing it, you need to install switches on the board. Since different boards have their own types of switches, to install the desired switch you must have documentation for the board.

Typically, when you purchase a motherboard, it already has L2 cache memory of 256, 512, 1 MB of memory. However, some boards may have sockets for installing microcircuits. Thus, a COAST (Cache On A Stick) connector can be installed, which currently does not have established standards, so memory from different manufacturers may not match each other and not be inserted into the socket. It is best to buy the motherboard along with the memory. The second type of socket is called CELP (Card Edge Low Profile).

Chips for cache memory, just like RAM, are divided into banks, of which there can be more than one. The bank must contain memory corresponding to the width of the system bus, and the maximum volume is limited by the capabilities of the motherboard. The installed microcircuits must be of the same type, and many parameter settings are set through the BIOS.

Sync SRAM(Synchronous Static RAM - synchronous static RAM), or Sync Burst SRAM, or SB SRAM - memory optimized for batch operation mode, operates with an access time of 8.5-13.5 nsec. It has a 3-2-2-2 diagram at a system bus frequency of more than 75 MHz, and 2-1-1-1 at a lower frequency.

PB SRAM(The Pipelined Burst Static RAM - pipelined burst static RAM) - the most modern type of memory, is a development of Sync SRAM.

Async SRAM(Asynchronous Static RAM - asynchronous static RAM) - the oldest type of memory with access time from 12 to 20 nsec with a 3-2-2-2 diagram at a bus frequency of more than 33 MHz. Since it does not support synchronous access, the performance is low.

When accessing RAM, it checks for data in the cache memory (which acts almost like a buffer), which stores the most frequently used data for programs. This data is duplicated because it resides in both RAM and cache memory.

For 16 MB of RAM, 512 KB of cache memory is sufficient. Cache memory is more expensive than RAM and is therefore used for specific purposes. Of course, it would be possible to use ultra-fast memory as RAM, but it is more expensive than the existing one, and since during operation all the memory is not used almost simultaneously, but only some of its parts, then by using cache memory we can significantly increase the power of the computer.

The type of cache memory is determined by the motherboard or is set using jumpers; using switches, you can set it size. The cache itself can be disabled using the BIOS.

Random access memory is a random access memory (RAM) in which, during operation, computer equipment executable input, output and intermediate data processed are stored.

During the startup process of the operating system, the RAM contains program and OS data. The amount of RAM directly affects the solution of simultaneously running tasks. That is, the larger the amount of RAM, the more tasks the computer can handle. It is also very often used by a video card as video memory.

Types of RAM

To date, four types of RAM have been released: DDR, DDR2, DDR3, DDR4. They are also divided into 2 form factors: DIMM - for computers, SO-DIMM - for laptops. These two types are completely different, they cannot be confused; for computers they are elongated, for laptops they are short. Let's look at each generation of RAM separately.

DDR- the first type of memory, it is more than 20 years old. Uses 2.6V voltage. DDR SDRAM Specifications:

Module name	Chip type	Memory bus frequency, MHz
PC1600	DDR200	100
PC2100	DDR266	133
PC2400	DDR300	150
PC2700	DDR333	166
PC3200	DDR400	200
PC3500	DDR433	217
PC3700	DDR466	233
PC4000	DDR500	250
PC4200	DDR533	267
PC5600	DDR700	350

DDR2- the second generation of RAM, first appeared in 2003. Uses 1.8V voltage. DDR2 Specifications:

Module name	Type	Memory bus frequency, MHz
PC2‑3200	DDR2‑400	200
PC2‑4200	DDR2‑533	266
PC2‑5300	DDR2‑667	333
PC2‑5400	DDR2‑675	337
PC2‑5600	DDR2‑700	350
PC2‑5700	DDR2‑711	355
PC2‑6000	DDR2‑750	375
PC2‑6400	DDR2‑800	400
PC2‑7100	DDR2‑888	444
PC2‑7200	DDR2‑900	450
PC2‑8000	DDR2‑1000	500
PC2‑8500	DDR2‑1066	533
PC2‑9200	DDR2‑1150	575
PC2‑9600	DDR2‑1200	600

DDR3- This is the third generation, and it is divided into three types with different voltages: DDR3 - 1.5V, DDR3L - 1.35V, DDR3U - 1.25V. Release of all modifications from 2007 to 2010. DDR3 Specifications:

Module name	Type	Memory bus frequency, MHz
PC3‑6400	DDR3‑800	400
PC3‑8500	DDR3‑1066	533
PC3‑10600	DDR3‑1333	667
PC3‑12800	DDR3‑1600	800
PC3‑14900	DDR3‑1866	933
PC3‑17000	DDR3‑2133	1066
PC3‑19200	DDR3‑2400	1200

DDR4- This is the latest generation today; it entered mass production in 2014. Voltage consumption 1.2V. Has a larger number of different timings. DDR4 Specifications:

Module name	Type	Memory bus frequency, MHz
PC4-12800	DDR4-1600	800
PC4-14900	DDR4-1866	933.33
PC4-17000	DDR4-2133	1066.67
PC4-19200	DDR4-2400	1200
PC4-21333	DDR4-2666	1333
PC4-23466	DDR4-2933	1466.5
PC4-25600	DDR4-3200	1600

As you probably noticed, each subsequent generation consumes less energy, but produces more high performance. This ensures efficient operation and minimal energy consumption.

How to increase RAM

In principle, there is nothing complicated here. To increase RAM, first turn off the computer's power supply using the button or unplug the power cable from the network; we take it out from the laptop Charger, we're filming battery. We open the case of the computer or laptop, on the motherboard near the RAM modules the form factor of the RAM is indicated, from it you can understand what type of memory your device supports. But I recommend removing the module installed in your PC and looking at the generation, type, name and choosing one similar to your characteristics.

As for increasing DDR3 RAM. All motherboards that support DDR3 also support DDR3L, but not vice versa. That is, motherboards released for DDR3L do not support DDR3 RAM.

RAM diagnostics

If the memory module is damaged, the operating system Windows system starts to malfunction and generate various errors. In such cases, it is necessary to diagnose all computer components. In this article, I will tell you how to diagnose RAM.

Diagnostics using MemTest86+

The most common program for diagnosing a random access memory device among masters is MemTest86+. Download and create (you can use any other program). Set this bootloader to first place or using Boot Menu choose your media.

MemTest86+ will load and automatically begin diagnosing all RAM modules. There are 10 tests in total, each starting from the beginning. If even one error appears, then turn off the device, remove all modules, leaving only one strip. Now diagnose each one individually to identify the faulty one. To see what a malfunction looks like in the Memtest program, see the picture below. The error may also show itself as various incidents displayed on the screen.

When the test is complete, press ESC to exit.

I hope this article has brought clarity to many readers on RAM issues. Use the form below to subscribe to new articles and share with friends. Thank you for your attention, see you next time!

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Greetings, dear readers! Today I will talk about the types of computer RAM. There are many varieties of it - enough to get confused in the parameters.

From this article you will learn:

A brief excursion into history

A long time ago, when computers were large, programs were small, and viruses did not exist at all, SIMM modules of several modifications were used: 30, 68 and 72 pins. They worked in conjunction with processors from 286 to 486 inclusive.

Now it is extremely difficult to find such a computer in working condition: there is no modern software for it. Programs that could theoretically be launched turn out to be too cumbersome in practice.

DIMM

The main difference from its predecessor is that the contacts located on both sides of the strip are independent, unlike the paired contacts on SIMM. SDRAM technology is already involved here - synchronous dynamic random access memory.
Mass production of this type of memory began in 1993. Such modules were intended primarily for the Intel Pentium or Celeron processor on a 64-bit data bus.

SO-DIMM memory modules are more compact as they are used in laptops.

DDR

More precisely, this type of memory is correctly called DDR SDRAM. It appeared on the market in 2001 and was used as RAM and video memory. The difference from its predecessor is the double frequency, since the bar is capable of transmitting data twice in one clock cycle.

This is the first type of memory module that can operate in dual-channel mode.

You can find out more about what dual-channel mode is.

And so yes, DDR SDRAM and its descendants are produced in the DIMM form factor, that is, they have independent contacts on both sides.

DDR2

This type of memory was able to compete with its predecessor already in 2004 and occupied a leading position until 2010. The sticks were produced in DIMM form factors for desktop computers and SO-DIMM for portable ones.

Compared to its predecessor, this type of memory has:

• Greater throughput;
• Less energy consumption;
• Improved cooling thanks to design.

The disadvantages include higher RAM timings. What it is .

DDR3

Like its predecessor, they are produced in the form of a 240-pin strip, but are incompatible due to different connectors (I’ll talk about this in more detail later).

The memory type is characterized by an even higher frequency and lower power consumption, as well as an increase in pre-swapping from 4 to 8 bits. There is a DDR3L modification with an operating voltage reduced to 1.35 V. By the way, about frequency. There are several modifications: 1066, 1333, 1600, 1866, 2133 or 2400 with the corresponding data transfer speed.
Produced since 2012. Computers using this type of memory are still in use today. The volume of installed modules is from 1 to 16 GB. In the SO-DIMM form factor, the “ceiling” is 8 GB.

DDR4

The fourth generation doubled the number of internal banks, thereby increasing the transfer speed of the external bus. Mass production began in 2014. The top models have a throughput of up to 3,200 million transmissions per second, and are available in modules ranging from 4 to 128 GB.

They already have 288 contacts. The physical dimensions of the part are the same, so the connectors are packed more tightly. Compared to DDR3, the height has been slightly increased.
SO-DIMMs have 260 pins located closer together.

What's next?

An interesting trend: with each next generation of memory, the timings increase, which engineers try to compensate for by increasing the operating frequency and data transfer speed. So effective that the next generation turns out to be faster than its predecessors.

That is why I once again draw your attention to the fact that when choosing components, try to “dance” from the DDR4 standard as the newest and most progressive.

Memory type compatibility

There is a misconception that, due to the interface features, it is impossible to insert a memory stick into unsuitable slots. I will say this: a strong enough guy (and even some girls) will insert anything anywhere - not only RAM, but also Intel processor into the AMD slot. True, there is one BUT: such an assembly, alas, will not work.

Other users who carefully assemble computers usually cannot insert the RAM into the wrong slot. Even if the planks have the same dimensions, this will not allow making a so-called key. There is a small protrusion inside the slot that prevents mounting the wrong type of RAM. The appropriate strip has a small cutout in this place, so you can insert it without any problems.

How to determine the model

Built in Windows utilities allow you to find out only minimal information - the volume installed memory. It is impossible to find out what type it is this way. Third-party software will come to the rescue, providing complete information about the system - for example, Everest or AIDA64.

The memory type is also specified in the BIOS. Where exactly this information is indicated and how to call the BIOS depends on its modification. In most cases, it is enough to hold down the Del button when starting the computer, but exceptions are possible.

Naturally, the marking is indicated on the RAM itself, or rather on the glued nameplate. To get to the bar, you will have to disassemble the case and dismantle it. In the case of a laptop, this simple task turns into a fascinating quest with viewing detailed instructions for disassembly.

Here, in fact, is all about the types of RAM, which is enough to know to independently select components. And if you are building a gaming computer, I recommend that you read the information.

Thank you for your attention and see you next time! Don't forget this blog and share posts on social networks.

Memory modules are an evolutionary development of individual memory chips (DIPs) previously used on PCs. Initially, memory on PCs was installed in separate chips. Due to their physical designs, they were often called dual integrated package (DIP) chips. For these individual chips, the original IBM XT and AT systems had 36 sockets on the motherboard. On bus-connected memory cards, you could often find even more sockets. That is, working on boards with these chips used to take hours.

PC memory modules

In addition to the long and labor-intensive work with installing memory, DIP chips had one problem - over time, when the system went through thermal cycles, they crawled out of their sockets. Every day, as the PC was turned on and off, the system warmed up and cooled down, and the chips gradually came out of the sockets - a phenomenon called chip creep. Eventually, good contact was lost and memory errors appeared. Fortunately, reinstalling all the chips in their sockets usually fixed the problem, but if you were servicing many systems, this method was time-consuming.

At that time, the alternative to this was to solder the memory on or an expansion card. This prevented the chips from creeping and made the connection more permanent, but caused another problem. If something happened to the chip, you had to unsolder the old one and solder in a new chip, or dispose of the motherboard/memory card along with the chip. This was expensive and made troubleshooting memory problems difficult.

The chip must be both soldered and removable, which became possible by using memory modules instead of separate chips. The first modules had a single row of electrical contacts and were called single integrated memory modules (SIMMs). Whereas later modules had two rows and were called Dual Modular Memory Modules (DIMMs) or Rambus Integrated Memory Modules (RIMMs). These small boards were connected to special connectors on the motherboard or memory card. Individual memory chips were soldered to the module, so removing and replacing them was impossible. Instead, if a problem occurred, you had to replace the entire module. This module was treated as one large memory chip.

Several types of SIMMs, DIMMs, and RIMMs are widely used in desktop systems. The difference between types is often characterized by the number of their contacts, the width of the row or the type of memory.

For example, SIMMs are available in two main physical types: 30-pin (8 bits plus option for 1 additional bit) and 72-pin (32 bits plus option for 4 additional bits) - with varying capacities and other technical characteristics. 30-pin SIMMs are physically smaller than the 72-pin versions. Either version may have chips on one or both sides. SIMMs were widely used from the late 1980s to the late 90s, but have become obsolete.

DIMMs are available in five main types. SDR (Single Data Rate) DIMMs have 168 pins with one notch on both sides and two notches along the contact area. DDR DIMMs have 184 pins, two notches on each side, and only one offset mark along the pin area. DDR2 and DDR3 DIMMs have 240 pins, two notches on each side and one near the center of the contact area. DDR4 DIMMs have 288 pins, two notches on each side (the cutouts are squarer than previous DIMM designs) and one near the center of the contact area.

All memory DIMMs are either 64 bits (non-ECC/parity) or 72 bits (data plus parity or error correction code). The main physical difference between SIMMs and DIMMs is that DIMMs have dissimilar signal pins on each side of the module, resulting in two rows of electrical pins. That's why they are called dual embedded memory modules, with only 1 inch of extra length they have many more pins than SIMMs.

Note. Regarding memory modules, there is confusion among users and even in the industry regarding the terms: single-sided and double-sided. The single- or double-sided designation actually has nothing to do with the physical location of the chips on one or both sides of the module. And it has nothing to do with whether SIMM is a module or DIMM (one- or two-line connecting contacts). Instead, the terms single-sided and double-sided indicate whether a module has one or two internal banks (called ranks) of memory chips installed.

A dual-rank DIMM has two full 64-bit banks of chips logically arranged so that the module is twice as large (has twice as many 64-bit rows). In most (but not all) cases, this requires chips on both sides of the module. Thus the term double-sided often indicates that the module has two rows, although this term is technically incorrect.

Single-row modules (incorrectly called single-sided) can also have chips physically mounted on both sides of the module. And modules with two rows can have chips physically mounted on only one side. Instead, it is more convenient to use the terms “single row” or “double row” because they are much more precise and clearer.

The following figures show a typical 30-pin (8-bit) SIMM, 72-pin (32-bit) SIMM, 168-pin SDRAM DIMM, 184-pin SDRAM (64-bit) DIMM, 240-pin DIMM, 240-pin DDR3 DIMM, 288-pin DIMM and 184-pin RIMM modules. The pins are numbered from left to right and are connected to both sides of the SIMM. The pins on a DIMM are different on each side, but on a SIMM each side is the same as the other and the connections go all the way through.

Please note that all dimensions are in both inches and millimeters (in parentheses), and modules are typically available in ECC versions with 1 additional ECC (or parity) bit for every 8 data bits (multiples of 9 in data width) or versions , which do not include ECC support (multiples of 8 in data width).

Typical 30-pin SIMM.

Typical 168-pin SDRAM DIMM

All of these memory modules, considering the volume they store, are quite compact, and are available in several capacities and speeds. The table below lists the different capacities available for SIMM, DIMM and RIMM.

SIMM, DIMM and RIMM capacity

Volume	Standard Depth×Width	Parity/ECC Depth×Width
30-pin SIMM
256KB	256K×8	256K×9
1MB	1MBx8	1MBx9
4MB	4MBx8	4MBx9
16MB	16MBx8	16MBx9
72-pin SIMM
1MB	256K×32	256K×36
2MB	512K×32	512K×36
4MB	1M×32	1M×36
8MB	2M×32	2M×36
16MB	4M×32	4M×36
32MB	8M×32	8M×36
64MB	16M×32	16M×36
128MB	32M×32	32M×36
168/184 pin DIMM/DDR DIMM
8MB	1M×64	1M×72
16MB	2M×64	2M×72
32MB	4M×64	4M×72
64MB	8M×64	8M×72
128MB	16M×64	16M×72
256MB	32M×64	32M×72
512MB	64M×64	64M×72
1.024MB	128M×64	128M×72
2,048MB	256M×64	256M×72
240-pin DDR2/DDR3 DIMM
256MB	32M×64	32M×72
512MB	64M×64	64M×72
1.024MB	128M×64	128M×72
2,048MB	256M×64	256M×72
4,096MB	512M×64	512M×72
8,192MB	1.024M×64	1.024M×72
288-pin DDR4 DIMM*
4,096MB	512M×64	512M×72
8,192MB	1.024M×64	1.024M×72
184-pin RIMM
64MB	32M×16	32M×18
128MB	64M×16	64M×18
256MB	128M×16	128M×18
512MB	256M×16	256M×18
1.024MB	512M×16	512M×18

• Higher capabilities available for servers

Memory modules of each type and capacity are available with at different speeds. To select the correct speed and memory type for your system, consult your motherboard documentation. If your system requires a memory module of a certain speed and the one specified is not available, you can almost always replace it with a faster one. As a rule, if you use modules equal to or greater than the system requirements, moving them will not cause any problems. Since there is little price difference between modules with different speeds, it makes more sense to buy faster ones than is necessary for a particular application, especially if they are the same price as slower memory modules. This may make them more suitable for use in a future system where faster speeds may be required.

Attention. Because SDRAM and newer memory modules have a built-in SPD-ROM that reports its speed and timing parameters to the system, most systems run the memory controller and memory bus at the speed corresponding to the slowest module installed.

Note. A bank is the smallest amount of memory required to form one memory line addressed by the processor. This is the minimum volume physical memory, which the processor reads or writes at a time and typically corresponds to the width of the processor's data bus. If the processor has a 64-bit data bus, the memory bank is also 64-bit. If the memory operates in two- or three-channel mode, a virtual bank is formed that is two or three times the absolute width of the processor data bus.

It is not always possible to replace a module with a larger capacity unit and expect it to work. Many systems, by design specification, have limitations in the maximum usable module capacity. A higher capacity module only works if the motherboard is designed to accept it in the first place. To determine the correct power and speed of use, refer to your system's documentation.

On some systems, the upgrade allows the use of modules with higher bandwidth and/or more high speed, than was intended for this system. Go to the system manufacturer's website and see if a BIOS update is available.

How to choose RAM (RAM, DDR), which memory module is better

When choosing RAM (RAM, DDR) for upgrading a computer, or assembling a new one, most users pay little attention to the quality and type of RAM modules. The “only parameter” of RAM is often its capacity, but this is far from the only parameter that you need to pay attention to when choosing. And so, let's consider basic RAM parameters, and what depends on them.

Form factor

For a desktop computer, the form factor (standards and physical dimensions) will be DIMM, and for a laptop SODIMM.

Well, now let's get down to the characteristics...

Amount of RAM and number of memory modules

As stated earlier, this is the first criterion for selection. When choosing the volume of RAM modules and their quantity, you must first of all clearly understand for what purposes the computer will be used.

If this is a computer for office tasks or surfing the Internet, then it does not need large volume RAM, and today, for such a computer, it will be enough 2GB one module.

If your computer is a gaming station, or a workstation with applications that consume a large amount of RAM, then it would be advisable to purchase 4 - 8 GB

Number of RAM modules significantly affects PC performance. Here, for example, the same computer with the same amount of RAM, but with big amount memory modules (for example, the first one has 4GB with one stick, and the second one has 2 sticks of 2GB each) will load the game faster than the first one. "Why is that?" - you ask, but because modern motherboards, just like memory controllers in processors, have support two or three channel memory modes. By installing 2 or 3 RAM sticks in the corresponding slots of the motherboard (to activate this mode, the sticks must be inserted into slots of the same color), you will activate two or three channel mode, which in theory can increase the total memory bandwidth by 2 or 3 times, respectively ( in practice it is much less, but the difference is significant). For example, if one memory module has a bus width of 64 bits, this means that the processor can read 64 bits from memory in one clock cycle, and the number of clock cycles corresponds to the operating frequency of the RAM. And when you set two or three channel mode, you thereby increase the bus width by 2 (128 bits) or 3 (192 bits) times.

But there are some here too underwater rocks, you should not immediately rush to buy several RAM modules if this performance gain does not play a big role for you. By installing two or three channel mode, you may reduce the stability of the computer, since the likelihood of errors in such modes is much higher than in single-channel mode. This depends on many factors: operating frequency, manufacturer, timings, whether the memory modules that need to work together are the same, etc. Moreover, from my experience in computer repair, there are many cases when, after 3 - 4 years of uninterrupted operation in dual-channel mode, the motherboard (chipset) gradually (and sometimes abruptly) stops working correctly in this mode, or does not start at all (the latter option is more frequent) reporting the absence of memory modules. But as soon as all the modules except one were pulled out, the system magically began to work. This problem could be solved by installing two modules on one channel (of different colors), and “throwing out” the remaining modules (if there were any). Or you could warm up the chipset/processor (depending on where the memory controller is) - this could help for a short period of time. The reason why the memory controller fails, as well as the quality of the modules themselves deteriorates, is chip degradation.

Memory should be purchased based on the recommendations of the manufacturer of your computer’s motherboard. To do this, just go to the manufacturer’s website, find your board there, and find the section with supported modules and memory manufacturers. A motherboard can, of course, work wonderfully with other memory modules, but still, by purchasing memory from the list of supported ones, you guarantee stable operation.

Memory type and memory frequency

The type of RAM primarily indicates technical process, according to which the chips are made, and indicates that the newer module operates at a higher frequency, which has a positive effect on performance.

On this moment, there are 2 types of memory - DDR2 and DDR3, to buy a new computer, I think the choice is obvious - take only new ones, and this is DDR3 (at the time of writing). To upgrade your computer, you don’t have much of a choice; you’ll have to take the memory that your motherboard supports. Only in some cases, when upgrading a computer, you can change the memory to a newer one. But this is only possible if you have a “combo” motherboard that supports both older and newer types of memory, but together, modules of different types will not work, and if you have more old memory, then you will have to “throw it out” and put a newer one in other slots.

The frequency of RAM can be different; sticks of even the same type can be different frequencies. Ideally, it is advisable to choose memory with a frequency identical to the processor FSB bus. And do not confuse the effective frequency of RAM operation with the effective one. For example, DDR 1333 memory is DDR2 class memory and operates at a REAL frequency of 667 MHz. The FSB bus of the processor is also described as effective, and it must be divided by 2 to determine the real one.

Memory delays (timings)

Memory timings or memory latency are time delays in a signal. Memory latencies in some way affect the performance (bandwidth and access speed) of the RAM module as a whole. The lower the memory latency, the faster it can run. Memory timings are usually written in the form 2-2-2-6, each part of the recording corresponds to the signal delay of each of the main parameters. We won’t go into the details of how each process works right now, you just need to know that the lower the memory timings, the more productive it is (up to 10%).

For modern memory modules, its timings are not the main criterion, since processors working with DDR3 memory have a relatively large second- and third-level memory cache, which can significantly reduce the number of memory accesses and, in turn, reduces the value of memory latencies. But despite this, timings still matter and cannot be ignored when choosing a memory module.

RAM module manufacturer

The stability, quality, and to some extent performance of RAM directly depend on the manufacturer. Not all RAM manufacturers make high-quality memory modules, and as a rule, a high-quality memory module costs a little more than others. I will give a few well-known and good producers memory at the moment: Transcend, Samsung, Kingston, OCZ. These are not the only manufacturers who do good memory, but when buying memory from these manufacturers you do not risk buying a pig in a poke.

Overclocking

Most well-known manufacturers have overclocked RAM models. This undoubtedly gives an increase in performance, but you shouldn’t overpay significantly for it, since you can overclock the RAM yourself. And besides, this will lead to her death faster due to the degradation of the chips. But if you still decide to choose an overclocked module, then please note that these memory modules must have cooling.

Cooling

If you plan to overclock your computer, including RAM, then it is advisable to choose a memory module that has cooling in the form of aluminum plates.

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