SIMM, DIMM, DDR and others - how to distinguish RAM modules by appearance? RAM.

In most computer electronics stores, the first thing a customer who comes to buy RAM strips will be simply asked where he is going to insert them. It is the scope of application that is the main difference between DIMM and SODIMM, and specifications- details that are no longer very significant for the average person.

It’s not difficult to figure this out: the form factor of DIMM memory modules is designed for installation in full-size desktop systems, SODIMM is placed in cases of laptops, office equipment and other compact systems. Both the first and second types are a printed circuit board with contacts and DRAM memory microchips.

What do we see when we look away from system unit full tower on a laptop or mini-ITX? Significant difference in size. Naturally, in small cases there is limited space for components, so they are made miniature whenever possible. Basics physical difference DIMM from SODIMM - increased length and, as a result, more contacts.

Comparison

This is what DIMM and SODIMM RAM strips look like in comparison:

It is immediately noticeable how shorter the modules designed for compact systems are. The form factor is strictly regulated, so the length of all DIMMs, regardless of memory type, is 133.35 mm, and SODIMM is 67.6 mm.

Memory modules must have key slots that block installation in an unsuitable interface, as well as cutouts for attaching port latches. SODIMM has one at each end, they are located 20 mm from the edge with the contacts. DIMMs have two, one at a height of 9.5 mm, the other at 17.3 mm (for current DDR3).

DIMM modules have more pins: for DDR3 their number is 240 pins versus 204 for SODIMMs, for DDR4 – 288 pins and 260 pins, respectively. Other technical characteristics of RAM strips depend on specific model: memory timings, operating frequency, capacity can be almost anything.

Some time ago, the answer to the question, what is the difference between DIMM and SODIMM, almost always included an indication of the supply voltage. Indeed, in the past, most compact systems supplied 1.35 V to RAM to optimize power consumption, while full-size modules required 1.5 V. Today, although this distinction remains for some models, most DDR3 sticks are powered from 1.5 V regardless form factor.

Hello, friends. Next up is our extremely important component stationary personal computer. RAM is considered one of the basic parts of absolutely any electronic device. computing complex. And today we will tell you about RAM strips for traditional desktop systems. To be more precise, our focus is on a removable dynamic rewritable memory module of the DIMM DDR3 standard (240 pins). Generally, DIMM memory module DDR3 has much in common with its “younger” modification of RAM boards for mobile PCs in the SO-DIMM format. Memory sticks of the DIMM DDR3 form factor have whole line specific properties. About the most significant parameters of this type digital devices you can find out in this publication.

Memory DIMM DDR3 - this is the third generation of full-size operational modules ultra-fast memory For desktop computers. Unlike previous RAM sticks with type DDR memory 2, this release of devices is characterized by double data transfer speed. This solution made it possible to achieve a significant increase in productivity in both traditional and mobile computer systems Oh. Thanks to a number of successful technical solutions, quickly rewritable DDR3 class memory can be equipped with a large capacity virtual memory(2 GB, 4 GB, 8 GB). Moreover, the frequency of this used memory has also become higher. Now on the shelves of electronics stores, ordinary users of computer systems are able to purchase modern modules RAM with operating frequency from 1333 to 2400 MHz.

Not everyone knows, but in a personal computer with a modern motherboardDIMM memory module DDR3 capable of working according to several unique schemes. We are talking about multi-channel (2, 3, 4) modes of operation of RAM modules. Besides reduced energy consumption, this popular type of RAM will give a significant increase in the performance of your computer assembly. We would like to reveal the principle of operation of this technology using the example of the available dual-channel mode. To obtain the maximum possible speed of information exchange between RAM strips and system board it is necessary to install absolutely identical devices in the corresponding (same color) slots on the motherboard. It is worth noting that your soldered boards must have the same main characteristics.

If you become the owner of a new motherboard, you probably might have noticed that there are not just one, but several special connectors for connecting modules RAM memory. But that doesn't mean you have to fill all the slots. For the average user home computer One or two sticks of RAM with a total memory size of 8 gigabytes will be quite enough. Using the 2-channel method of RAM operation, as additional method After upgrading the system, you will have access to the remaining empty slots on the main PC board. In the future, you will only need to buy new devices and improve the configuration of your computer equipment.

Be careful - DIMM DDR3 RAM is not compatible with motherboards that work with the outdated DDR2 memory type. About the mismatch between the RAM module and connectors system bus They will tell you a special key (contact cable with a groove). On the sides of any RAM device you can find small recesses with which they are attached to the main board of a personal computer. This technical trick does not give us a chance to install in computer assembly a RAM memory device that is not suitable for our system.

Memory DIMM

DIMM (SDRAM , Synchronic DRAM, Dual In line Memory Module, - "synchronous DRAM" - dynamic RAM with synchronous interface. SDRAM - "first generation" synchronous memory, have throughput about 100 Mb/s and is a memory module with two rows of contacts. Externally similar to SIMMs. Synchronization distinguishes SDRAM from those operating on an asynchronous interface (FPM/EDO/BEDO DRAM).

In addition to the synchronous access method, SDRAM uses an internal division of the memory array into two independent banks (that is, they have separate contacts - usually 2x84), which allows you to increase the bit capacity - i.e. As a result, combine selection from one bank with setting up an address in another bank. SDRAM also supports block swapping.

It is used both in IBM-compatible PCs (mainly boards for Pentium III), and in Apple computers. It is also possible to install SDRAM for the processor Intel Pentium 4 (there is an i845 chipset with support of this type memory).

Unlike SIMM, a DIMM is pressed into the connector and “covered” with levers, with the help of which it is pulled out.

Presence of the word dial means independence of contacts on both sides. All varieties of conventional DIMMs have the same (168) number of pins (168, designed for a 64-bit bus width) and form factor, and differ only in the “keys” (cuts on the sides).

Install modules DIMM together with modules like SIMM(i.e. together on m/b) is not recommended due to the fact that DIMMs are powered by 3.3 volts, and SIMMs by 5. Moreover, most motherboards have a common power supply for SIMM and DIMM slots. In this regard, when installing modules in both types of slots, the DIMM will be supplied increased voltage 5 volts (may damage chips).

Numbers - this is both the specification (for example, PC 100 standard) and the operating frequency of the module (for example, 100 MHz). Many older motherboards can also use frequencies of 75 MHz and 83 MHz, but at the user's own risk. Overclockers also used values ​​of 103, 112, 124 MHz. Application increased frequency tires and normal operation m/b-peripherals, as a rule, were not guaranteed by anyone.

The first complete specification for DIMM modules (these were PC-100) was released by Intel when preparing the i440BX chipset (with clock frequency system bus 100 MHz) in 1998.

The specification is still the most comprehensive of all memory module specifications currently available. Along with an addendum detailing EEPROM programming for SDRAM modules, it takes up more than 70 pages! The initial PC133 specification was also released by Intel at the end of 1999 and really differs from PC100 only in performance parameters. But back in November 1996. Intel officially sided with Direct Rambus, declaring that RDRAM will be the next standard after PC100 SDRAM. PC133 SDRAM supported by the company Via and taking into account the colossal problems of Rambus at that time (with the percentage of suitable chips being released) - it won.

Memory buses of 66 MHz and 100 MHz are obsolete. All PC133 modules contain chips with access times of 7.5 ns or less, which guarantees trouble-free operation at 133 MHz. The 133 MHz chips are compatible with all PC100 products. Minor differences between PC100 and PC133 have become reasons for deceiving consumers through non-standard labeling. Why buy new module PC133, if a used PC100 with an access time of 7 ns can also operate at 133 MHz? Modules with an access time of 7 ns or less are fully functional at 150 MHz. Here the selection criterion is the manufacturing quality of the entire DIMM module and the name of the manufacturer. That is, Brand's PC133 almost always keeps 150 MHz.

In addition to frequency, DIMM modules are divided by supply voltage and operating algorithm. Unbuffered modules with a supply voltage of 3.3 volts are standard. An unbuffered DIMM can contain memory like SDRAM, BEDO, EDO And FPM, have a data width of 64 or 72 bits for parity, and 72 and 80 bits for ECC.

These modules differ from the others in the positions of the keys (cuts) in the contact line. Those. If you look at the module from the front side (where the chips are), then the left key (cut) should be in the extreme right position, and the middle one should be in the middle position. The left key determines whether the module is buffered, and the middle one determines the supply voltage. Buffered DIMMs, are generally incompatible with non-buffered ones.

According to the JEDEC specification, DIMMs must implement PD technology. This is done using serial EEPROM and is called Serial Presence Detect (SPD). The ROM is an 8-pin chip located in the corner of a DIMM, and its contents describe the configuration and parameters of the module. Those. Visually, SPD is a small “extra” chip on the module.

Motherboards with some chipsets (eg 440LX/BX) can use SPD to configure the memory management system. Some motherboards can bypass the SPD by defining the module configuration in the usual way - this encourages some manufacturers to release ROMless DIMMs that do not meet the JEDEC specification.

Fame SPD received after a number of motherboards (for example, Intel AL440LX) refused to work with “consumer” DIMMs. In essence, this meant an Intel-inspired attempt to revive the use of PRD (now in the form of SPD). The 440LX checked not only the SPD itself, but also “information from the manufacturer”, for which a special closed standard was developed, so that even DIMMs with the correct SPD could be rejected by it. However, the attempt was not particularly successful, since the SPD control function is not used in all modern motherboards.

HSDRAM , Enhanced High Speed ​​SDRAM - enhanced high-speed SDRAM (DIMMs) at a bus frequency of 150 MHz and higher (depending on the type of chipset). Those. HSDRAM are higher quality chips than normal SDRAM. And before there were only "PC150" DIMM modules Kingmax. In September 2000 companies Enhanced Memory Systems(subdivision Ramtron International)And Mushkin announced the release of new SDRAM DIMM modules - with a frequency of 150 and a 2-3-2 setting (CAS, CAS-to-RAS, RAS, clock access time - 4.5 ns). Installation or timing is the response time of memory to various requests. HSDRAM modules will be able to operate with the same timings at frequencies up to 166 MHz. HSDRAM has no buffer and provides low latency, thereby achieving high performance. Theoretically, the memory bandwidth operating at 150MHz is 150MHz*8 bytes (since the bus width is 64 bits) = 1200MB/s (1.2GB/s). Well, compared to 1.066GB/s, the PC133 is very good. But the junior DDR PC1600 with its 1.6GB/s is still faster.

The gain of HSDRAM compared to hi-end systems based on PC-100 and Direct Rambus DRAM ranged from 28% to 49% (according to various indicators).

Small Outline DIMM, SO DIMM - a type of small DIMM designed primarily for laptop computers(notebooks, laptops) and sometimes for printers. The most common are 72- and 144-pin modules (32 and 64 bits, respectively).

Full name - 144pin SODIMM SDRAM and 72pin SODIMM SDRAM. 144-pin SO DIMMs have a "biased" voltage key, meaning the keys (and corresponding tabs) are offset lengthwise, making impossible to install"wrong" memory module, although it significantly complicated production.

GF1000 DIMM . Samsung Company develops new technology DRAM for GPUs. The memory code name is GF1000, memory bandwidth is 2-4 Gbit/s, supply voltage is 1.8 V. The memory will be available for sale in 2004.

Common types SDRAM And DRAM also called asynchronous - because setting the address, supplying control signals and reading/writing data can be performed at arbitrary times - it is only necessary to observe the timing relationships between these signals. These timing relationships include so-called guard intervals, which are necessary to stabilize signals that do not allow the theoretically possible memory speed to be achieved. There are also synchronous types of memory that receive an external clock signal, the pulses of which are strictly linked to the moments of address submission and data exchange; In addition to saving time on guard intervals, they allow more complete use of internal pipelining and block access.

Publication date:

25.06.2009

As you know, RAM contributes a large component to the performance of a computer. And it is clear that users are trying to increase the amount of RAM to the maximum.
If 2-3 years ago there were literally several types of memory modules on the market, now there are much more of them. And it became more difficult to understand them.

In this article we will look at various designations in the marking of memory modules so that it is easier for you to navigate them.

First, let's introduce a number of terms that we will need to understand the article:

• strip ("die") - a memory module, a printed circuit board with memory chips on board, installed in a memory slot;
• one-sided strip - a memory strip in which the memory chips are located on 1 side of the module.
• double-sided stick - a memory stick in which memory chips are located on both sides of the module.
• RAM (Random Access Memory, RAM) - random access memory, in other words - random access memory. This is a volatile memory whose contents are lost when power is lost.
• SDRAM (Synchronous Dynamic RAM) - synchronous dynamic random access memory: all modern memory modules have just such a device, that is, they require constant synchronization and updating of the content.

Consider the markings

• 4096Mb (2x2048Mb) DIMM DDR2 PC2-8500 Corsair XMS2 C5 BOX
• 1024Mb SO-DIMM DDR2 PC6400 OCZ OCZ2M8001G (5-5-5-15) Retail

Volume

The first designation in the line is the size of the memory modules. In particular, in the first case it is 4 GB, and in the second case it is 1 GB. True, 4 GB in in this case implemented not by one memory stick, but by two. This is the so-called Kit of 2 - a set of two planks. Typically, such kits are purchased to install strips in two-channel mode into parallel slots. The fact that they have the same parameters will improve their compatibility, which has a beneficial effect on stability.

Type of shell

DIMM/SO-DIMM is a type of memory stick housing. All modern memory modules are available in one of the two specified designs.
DIMM(Dual In-line Memory Module) - a module in which the contacts are arranged in a row on both sides of the module.
Memory DDR type SDRAM is available in the form of 184-pin DIMM modules, and 240-pin strips are available for DDR2 SDRAM memory.

Laptops use smaller memory modules called SO-DIMM(Small Outline DIMM).

Memory type

Memory type is the architecture by which the memory chips themselves are organized. It affects all technical characteristics of memory - performance, frequency, supply voltage, etc.

On this moment 3 types of memory are used: DDR SDRAM, DDR2 SDRAM, DDR3 SDRAM. Of these, DDR3 is the most productive and consumes the least energy.

Data transfer frequencies for memory types:

• DDR: 200-400 MHz
• DDR2: 533-1200 MHz
• DDR3: 800-2400 MHz

The number indicated after the memory type is frequency: DDR400, DDR2-800.

Memory modules of all types differ in supply voltage and connectors and cannot be inserted into each other.

The data transfer frequency characterizes the potential of the memory bus to transfer data per unit time: the higher the frequency, the more data can be transferred.

However, there are other factors, such as the number of memory channels and memory bus width. They also affect the performance of memory subsystems.

To comprehensively evaluate the capabilities of RAM, the term memory bandwidth is used. It takes into account the frequency at which data is transmitted, the bus width and the number of memory channels.

Bandwidth (B) = Frequency (f) x memory bus width (c) x number of channels (k)

For example, using DDR400 400 MHz memory and a dual-channel memory controller, the bandwidth will be:
(400 MHz x 64 bit x 2)/ 8 bit = 6400 MB/s

We divided by 8 to convert Mbit/s to MB/s (there are 8 bits in 1 byte).

Memory module speed standard

To make it easier to understand the speed of the module, the designation also indicates the memory bandwidth standard. It just shows what bandwidth the module has.

All of these standards begin with the letters PC and are followed by numbers indicating memory bandwidth in MB per second.

Module name	Bus frequency	Chip type
PC2-3200	200 MHz	DDR2-400	3200 MB/s or 3.2 GB/s
PC2-4200	266 MHz	DDR2-533	4200 MB/s or 4.2 GB/s
PC2-5300	333 MHz	DDR2-667	5300 MB/s or 5.3 GB/s 1
PC2-5400	337 MHz	DDR2-675	5400 MB/s or 5.4 GB/s
PC2-5600	350 MHz	DDR2-700	5600 MB/s or 5.6 GB/s
PC2-5700	355 MHz	DDR2-711	5700 MB/s or 5.7 GB/s
PC2-6000	375 MHz	DDR2-750	6000 MB/s or 6.0 GB/s
PC2-6400	400 MHz	DDR2-800	6400 MB/s or 6.4 GB/s
PC2-7100	444 MHz	DDR2-888	7100 MB/s or 7.1 GB/s
PC2-7200	450 MHz	DDR2-900	7200 MB/s or 7.2 GB/s
PC2-8000	500 MHz	DDR2-1000	8000 MB/s or 8.0 GB/s
PC2-8500	533 MHz	DDR2-1066	8500 MB/s or 8.5 GB/s
PC2-9200	575 MHz	DDR2-1150	9200 MB/s or 9.2 GB/s
PC2-9600	600 MHz	DDR2-1200	9600 MB/s or 9.6 GB/s

Memory type	Memory frequency	Cycle time	Bus frequency	Data transfers per second	Standard name	Peak Data Rate
DDR3-800	100 MHz	10.00 ns	400 MHz	800 million	PC3-6400	6400 MB/s
DDR3-1066	133 MHz	7.50 ns	533 MHz	1066 million	PC3-8500	8533 MB/s
DDR3-1333	166 MHz	6.00 ns	667 MHz	1333 million	PC3-10600	10667 MB/s
DDR3-1600	200 MHz	5.00 ns	800 MHz	1600 million	PC3-12800	12800 MB/s
DDR3-1800	225 MHz	4.44 ns	900 MHz	1800 million	PC3-14400	14400 MB/s
DDR3-2000	250 MHz	4.00 ns	1000 MHz	2000 million	PC3-16000	16000 MB/s
DDR3-2133	266 MHz	3.75 ns	1066 MHz	2133 million	PC3-17000	17066 MB/s
DDR3-2400	300 MHz	3.33 ns	1200 MHz	2400 million	PC3-19200	19200 MB/s

The tables indicate exactly the peak values; in practice they may be unattainable.

Manufacturer and its part number

Each manufacturer gives each of its products or parts its internal production marking, called P/N (part number).

For memory modules different manufacturers it looks something like this:

• Kingston KVR800D2N6/1G
• OCZ OCZ2M8001G
• Corsair XMS2 CM2X1024-6400C5

On the website of many memory manufacturers you can study how their Part Number is read.
Modules Kingston ValueRAM family:

Kingston HyperX family modules (with optional passive cooling for overclocking):

From the OCZ marking you can understand that this is a 1 GB DDR2 module with a frequency of 800 MHz.

By labeling CM2X1024-6400C5 It is clear that this is a 1024 MB DDR2 module of the PC2-6400 standard and CL=5 delays.

Some manufacturers indicate the time in ns of access to the memory chip instead of the frequency or memory standard. From this time you can understand what frequency is used.
This is what Micron does: MT47H128M16HG-3. The number at the end indicates that the access time is 3 ns (0.003 ms).

According to the well-known forum T=1/f frequency of the chip f=1/T: 1/0.003 = 333 MHz.
The data transmission frequency is 2 times higher - 667 MHz.
Respectively, this module DDR2-667.

Timings

Timings are delays when accessing memory chips. Naturally, the smaller they are, the faster the module works.

The fact is that the memory chips on the module have a matrix structure - they are presented in the form of matrix cells with a row number and a column number.
When accessing a memory cell, the entire line in which the desired cell is located is read.

First there is a choice the desired line, then the desired column. At the intersection of the row and column number the desired cell is located. Taking into account the huge volume of modern RAM, such memory matrices are not integral - for more quick access to memory cells they are divided into pages and banks.
First, the memory bank is accessed, the page in it is activated, then work takes place within current page: Select row and column.
All these actions occur with a definitely delay relative to each other.

Basic RAM timings are the delay between supplying the row number and column number, called time full access (RAS to CAS delay, RCD), the delay between supplying the column number and receiving the contents of the cell, called duty cycle time ( CAS latency, CL), delay between reading the last cell and submitting the number new line (RAS precharge, RP). Timings are measured in nanoseconds (ns).

These timings follow each other in the order of operations and are also indicated schematically 5-5-5-15 . In this case, all three timings are 5 ns, and the total duty cycle is 15 ns from the moment the line is activated.

The main timing is considered CAS latency, which is often abbreviated CL=5. It is he who “slows down” memory to the greatest extent.

Based on this information, you can wisely select the appropriate memory module.

RAM modules

RAM modules are manufactured on the basis of rectangular printed circuit boards with single-sided or double-sided arrangement of microcircuits. They differ in form factor and have different designs: SIMM (Single In-line Memory Module - memory module with single-row contacts); DIMM (Dual In-line Memory Module - memory module with double-row contacts); SO DIMM (Small Outline DIMM - small DIMM size). The contacts of the memory module connectors are coated with gold or an alloy of nickel and palladium.

ModulesSIMM is a board with flat contacts along one side; They are installed into the motherboard connector at an angle and then rotated to the working (vertical) position using latches. There are two types of SIMMs: 30-pin, 9-bit (8 data bits and 1 parity bit); 72-pin, 32-bit (no parity) or 36-bit (parity). Therefore, the 32-bit bus required the use of four banks of 30-pin SIMMs or one 72-pin module; for a 64-bit bus - two banks of 72-pin modules.

ModulesDIMM There are two types: 168-pin (for installing SDRAM chips) and 184-pin DIMMs (for DDR SDRAM chips). They are identical in installation dimensions, inserted into the connector motherboard vertically and fixed with latches. During the transition period, motherboards were equipped with connectors for both types of DIMM modules, but currently SIMM and 168-pin DIMM modules are outdated and not used in PCs.

ModulesSO DIMM with 72- and 144-pin connectors are used in portable PCs. They are installed into the motherboard in the same way as SIMM modules.

Currently, the most popular DIMM modules are DDR SDRAM, DDR2 SDRAM and DDR3 SDRAM chips.

DIMMs based on DDR SDRAM chips are available with 184 pins (Fig. 1).

Rice. 1. 184-pin DIMM board:

1 - DDR SDRAM chips; 2 - microcircuit buffer memory and error control; 3 - cutouts for mounting the board; 4 - key;

5 - connector

The key on the memory module is a cutout in the board, which, in combination with a corresponding protrusion in the motherboard connector, prevents the module from being installed the wrong way around. In addition, the key for incompatible RAM modules may have different placement (move between contacts in one direction or the other), indicating the supply voltage rating (2.5 or 1.8 V) and protecting against electrical damage.

Memory chips such as DDR2, DDR3, which replace DDR, are produced in the form of 240-pin DIMM modules.

Modern memory modules for PCs are supplied in 512 MB, 1.2 and 4 GB versions.

At the time of this writing, the market is dominated by third-generation DDR memory modules, or DDR3. DDR3 memory has higher clock speeds (up to 2400 megahertz), lower power consumption by approximately 30-40% (compared to DDR2) and correspondingly lower heat dissipation.

However, you can still find DDR2 memory and outdated (and therefore terribly expensive in places) DDR1 memory. All these three types are completely incompatible with each other, both electrically (DDR3 has lower voltage) and physical (see image). The necessary and sufficient amount of RAM depends on the operating system and application programs that determine the intended use of the PC. If you plan to use the computer for office or “multimedia” purposes (Internet, working with office applications OS Windows Vista and Windows 7 for comfortable work they require at least 1 GB of RAM, and when all graphic effects are enabled - up to 1.5 gigabytes.

Characteristics and markings of RAM

Consider the markings

Volume

The first designation in the line is the size of the memory modules. In particular, in the first case it is 4 GB, and in the second case it is 1 GB. True, 4 GB in this case is implemented not by one memory stick, but by two. This is the so-called Kit of 2 - a set of two planks. Typically, such kits are purchased to install strips in dual-channel mode in parallel slots. The fact that they have the same parameters will improve their compatibility, which has a beneficial effect on stability.

Type of shell

DIMM/SO-DIMM is a type of memory stick housing. All modern memory modules are available in one of the two specified designs.

Memory type

Memory type is the architecture by which the memory chips themselves are organized. It affects all technical characteristics of memory - performance, frequency, supply voltage, etc.

Data transfer frequencies for memory types:

DDR: 200-400 MHz

DDR2: 533-1200 MHz

DDR3: 800-2400 MHz

The number indicated after the memory type is the frequency: DDR400, DDR2-800.

Memory modules of all types differ in supply voltage and connectors and cannot be inserted into each other.

The data transfer frequency characterizes the potential of the memory bus to transfer data per unit time: the higher the frequency, the more data can be transferred.

However, there are other factors, such as the number of memory channels and memory bus width. They also affect the performance of memory subsystems.

Memory module speed standard

To comprehensively evaluate the capabilities of RAM, the term memory bandwidth is used. It takes into account the frequency at which data is transmitted, the bus width and the number of memory channels.

Bandwidth (B) = Frequency (f) x memory bus width (c) x number of channels (k)

For example, using DDR400 400 MHz memory and a dual-channel memory controller, the bandwidth will be: (400 MHz x 64 bit x 2) / 8 bit = 6400 MB/s

To make it easier to understand the speed of the module, the designation also indicates the memory bandwidth standard. It just shows what bandwidth the module has.

All of these standards begin with the letters PC and are followed by numbers indicating memory bandwidth in MB per second.

Timings

Timings are delays when accessing memory chips. Naturally, the smaller they are, the faster the module works.

The fact is that the memory chips on the module have a matrix structure - they are presented in the form of matrix cells with a row number and a column number. When accessing a memory cell, the entire line in which the desired cell is located is read.

First, the desired row is selected, then the desired column. At the intersection of the row and column number the desired cell is located. Taking into account the huge volume of modern RAM, such memory matrices are not solid - for faster access to memory cells, they are divided into pages and banks. First, the memory bank is accessed, the page in it is activated, then work takes place within the current page: selecting a row and column. All these actions occur with a definitely delay relative to each other.

The main RAM timings are the delay between the submission of the row number and the column number, called the full access time (RAS to CAS delay, RCD), the delay between the submission of the column number and receiving the contents of the cell, called the duty cycle time (CAS latency, CL), the delay between reading the last cell and supplying a new line number (RAS precharge, RP). Timings are measured in nanoseconds (ns).

These timings follow each other in the order of operations and are also designated schematically 5-5-5-15. In this case, all three timings are 5 ns, and the total duty cycle is 15 ns from the moment the line is activated.

The main timing is considered to be CAS latency, which is often abbreviated as CL=5. It is he who “slows down” memory to the greatest extent.

Based on this information, you can wisely select the appropriate memory module.

Manufacturer and its part number

Each manufacturer gives each of its products or parts its internal production marking, called P/N (part number).

For memory modules from different manufacturers it looks something like this:

Kingston KVR800D2N6/1G

• Corsair XMS2 CM2X1024-6400C5

On the website of many memory manufacturers you can study how their Part Number is read. Kingston ValueRAM family modules:

The latest marking says a lot, namely:

KVR - manufacturer Kingston ValueRAM

1066 – operating frequency (Mhz)

D3 - memory type (DDR3)

D (Dual) – rank/rank. A dual-rank module is two logical modules wired onto one physical channel and alternately using the same physical channel (needed to achieve the maximum amount of RAM with a limited number of slots)

8 – 8 DRAM memory chips

R – Registered, indicates stable operation without failures or errors for as long a continuous period of time as possible

7 – signal delay (CAS=7)

S – temperature sensor on the module

K3 – set (kit) of three modules

6G – the total volume of the kit (three strips) is 6 GB.

From the OCZ marking you can understand that this is a 1 GB DDR2 module with a frequency of 800 MHz.

From the markings of CM2X1024-6400C5 it is clear that this is a 1024 MB DDR2 module of the PC2-6400 standard and CL=5 latencies.

Some manufacturers indicate the time in ns of access to the memory chip instead of the frequency or memory standard. From this time you can understand what frequency is used. Micron does this: MT47H128M16HG-3. The number at the end indicates that the access time is 3 ns (0.003 ms).

According to the well-known forum T=1/f, the operating frequency of the chip is f=1/T: 1/0.003 = 333 MHz. The data transmission frequency is 2 times higher - 667 MHz. Accordingly, this module is DDR2-667.

Diagnosing possible problems with memory modules

A memory module consists of several chips located on one board. It is one of the most reliable computer components. In addition, it is very unlikely that modules with any defects will go on sale, since manufacturers carefully test them before sending them for sale. But such a possibility still exists, since even one manufacturer now produces a very large number of modules.

In a real situation, it is very easy to damage it. Just remember about static electricity. For example, it’s better not to try, having bought a 1GB memory module, insert it into the computer with one hand, and pet your cat with the other. In addition to static electricity, the performance of microcircuits is negatively affected by voltage drops in the network and a malfunction of the power supply. The same can be said about the thoughtless increase in the voltage supplying the memory during overclocking.

If your computer is located in a dusty or humid environment, this can damage the contacts in the memory connectors on the motherboard. The cause of the malfunction may be an increase in the temperature of the modules themselves and other components inside the case. If handled carelessly, you can simply physically damage the memory module. This is one of the reasons why we favor heatsinks on memory modules, they do not significantly reduce their temperature, but serve a good purpose in increasing durability.

A faulty memory module can present with many different symptoms. Let's try to highlight the most common ones:

Blue screens with error messages appear during Windows installations 98/2000/XP. This is one of the surest signs of memory problems.

Periodic malfunctions and appearance blue screens during Windows operation. The reason for this may not only be the memory, but also an increase in the temperature inside the case, so it is worth checking this possibility as well.

Crashes during memory-intensive operations: 3D games, tests, compilation, Photoshop, etc.

Inability to boot the computer. This may be accompanied by prolonged sound signals, with which the BIOS reports a memory problem. In this case, you will not be able to check the memory using diagnostic programs.

The only way to make sure that the problem is really in the memory is to change the module either yourself or at a service center.

To check this, turn off the computer, release the connector by opening the two latches, remove the module from the connector and carefully place it in the other slot, pressing the latches. After this, turn on the computer and repeat the test. If errors are detected again, then the module is faulty, and if there are no errors, then the connector is faulty.

– install memory modules with the same capacity;

– modules must match the operating frequency (Mhz), otherwise they will all operate at the frequency of the slowest memory;

– combine timings, memory latencies (delays);

– memory modules are better than one manufacturer and one model.

Basic rules for installing memory:

Carry out all work with the computer completely disconnected from the power supply, with dry hands;

Do not use excessive force - memory modules are very fragile!

Place the system unit on a strong and stable surface.

Step 1.

open the side cover of the system unit (for a standard vertical case, this is the left cover when looking at the system unit from the front). The number of OP slots is usually 2-6 connectors for most motherboards used in home computers. Before installation, pay attention to the video card - it may interfere with the installation of RAM. If it interferes, then temporarily dismantle it.

Step 2.

On the free slot selected for installing the RAM, unfasten the special latches on the edges.

open the side cover of the system unit (for a standard vertical case, this is the left cover when looking at the system unit from the front). Inside each connector there are small jumper keys, and on the contact part of the memory modules there are corresponding cutouts. Their mutual alignment prevents incorrect installation of memory or installation of modules of a different type. Each type has a different location and number of slots, and therefore, keys on the motherboard connectors (we already mentioned this when we talked about memory types).

Step 3.

Align the slot on the memory with the key in the motherboard slot (as shown in the image).

Step 4.

Insert the DIMM into the socket by pushing down on the top edge.

Step 5.

Press gently until the module is completely seated in the slot and the locking tabs on the edges of the slot are in place.

Step 6.

Make sure the retaining clips are in place and fully closed.

CONTROL QUESTIONS

Compare RAM modules: SIMM, DIMM and SO DIMM.

Diagram of a 184-pin DIMM.

What is the difference between memory modules of DDR, DDR2, DDR3 (oral) standards?

What is the sufficient amount of memory for a PC?

List the characteristics of memory that can be read in its labeling?

Memory bandwidth, how to calculate bandwidth?

What is timing? What is it measured in? How is it designated?

What is part number?

Decipher the marking indicated by the frame in the figure.

Decipher the markings:

4096Mb (2x2048Mb) DIMM DDR2 PC2-8500 Corsair XMS2 C5 BOX

1024Mb SO-DIMM DDR2 PC6400 OCZ OCZ2M8001G (5-5-5-15) Retail

List the most common memory module faults. Basic rules for installing memory ().

orally

PRACTICAL TASKS:

For the presented motherboard, select the appropriate RAM module.

Examine the module markings.