Hello friends! In this article we tried to answer numerous of your questions regarding RAM. ? How can I find out what RAM I have installed and how much? How to choose the right RAM for your computer. How do you know if your RAM is running in dual channel mode or not? What is better to buy, one 8GB DDR3 memory stick or two 4GB sticks each? And finally.
- If you are interested, or, also read our articles.
- Hello admin, one of my friends asks me to install more RAM. The computer properties show a capacity of 2 GB. We turned off the computer, opened the system unit, there was one stick of RAM, took it out, and there were no marks on it. Interestingly, it was not possible to determine the model of the motherboard. The computer was purchased a long time ago, so the question arose - how to find out the type of RAM it needs? After all, RAM differs in type, frequency and timing.
- Hi all! I wanted to buy additional RAM, I removed the cover of the system unit, took out the RAM stick and I can’t decipher the information written on it, the serial number is simply written there and that’s it. It is completely unclear at what frequency it operates and what type it is, DDR3 or DDR2. How to distinguish DDR3 memory from DDR2, how do they differ in appearance?
- I have one 4 GB DDR3-1600 RAM stick in the system unit, I want to install another 4 GB stick, but running at a higher frequency DDR3-1866. Will my computer work normally, and most importantly, in dual-channel mode?
My friend installed three RAM sticks of different sizes and frequencies into the system unit. Is this allowed? But what’s strange is that his computer works fine! - Tell me, how can I check if my RAM is working in dual-channel mode or not? And what conditions are needed for my memory to work in dual-channel mode. Same volume? Same frequency or same timings? How much faster does a computer run in dual-channel mode than in single-channel mode? They say that there is also a three-channel mode.
- What will work better, two sticks of 4 GB RAM in dual-channel mode or one stick, but with a capacity of 8 GB, respectively, the memory mode will be single-channel?
To find out all the information about a RAM module, you need to carefully examine it; usually the manufacturer labels the RAM with the proper information about the frequency, volume and type of RAM. If there is no such information on the module, then you need to find out everything about the motherboard and the installed processor; sometimes this action turns into a whole investigation.
- Important Notes: Friends, do not forget that all new processors Intel Core i3, Intel Core i5, Intel Core i7 The RAM controller is located in the processor itself (previously it was controlled by the north bridge of the motherboard) and the memory modules are now directly controlled by the processor itself, the same applies to the latest AMD processors.
- This means that it doesn't matter what RAM frequency your motherboard supports. It is important what RAM frequency your processor supports. If your computer has a processorIntel Core i3, Intel Core i5, Intel Core i7, then the officially supported memory standards of these processors: PC3-8500 (DDR3-1066 MHz), PC3-10600 (DDR3-1333 MHz), PC3-12800 (DDR3-1600 MHz), it is at these frequencies that your RAM will operate, even if the motherboard's passport indicates that the motherboard can work with PC3-19200 (DDR3-2400 MHz) high-frequency RAM memory sticks.
- It's another matter if your processor has unlocked multiplier, that is, with the letter “K” at the end, for example CPU Intel Core i7-4770 K, 3.5 GHz. An unlocked multiplier means that in a computer with such a processor you can install memory sticks of the highest frequency, for example DDR3-1866 MHz or DDR3-2400 MHz, such a processor can be overclocked and during overclocking the RAM will operate at its frequency of 2400 MHz . If you install the RAM stick DDR3-1866 MHz or DDR3-2400 MHz into a computer with a conventional processor, that is, with locked multiplier without letter" K” at the end, for exampleIntel Core i7-3770, 3.9 GHz then such a bar will work at best at a frequency DDR3-1600 MHz, and in the worst case, the computer will not boot. Therefore, buy RAM that is suitable for your processor.
- Regarding processorsAMD recent years, then they work with memoryPC3-10600 (DDR3-1333 MHz).
Firstly, the RAM stick itself should contain all the information you are interested in, you just need to read it correctly. I don’t argue, there are memory strips that have practically nothing on them, but we can handle them too.
For example, let’s take a Hynix RAM stick, it has the following information: 4 GB PC3 – 12800.
What does the following mean:
firstly, the volume is 4 GB,
secondly, 1Rx8 - Rank - a memory area created by several or all chips of a memory module, 1Rx8 are single-sided memory ranks, and 2Rx8 are double-sided memory ranks.
As you can see, this bar does not say that it is DDR2 or DDR3, but the throughput of PC3-12800 is indicated. PC3 is a designation for peak bandwidth belonging only to the DDR3 type (for DDR2 RAM the designation will be PC2, for example PC2-6400).
This means that our Hynix RAM stick is DDR3 and has PC3-12800 bandwidth. If the bandwidth of 12800 is divided by eight and you get 1600. That is, this DDR3 memory stick operates at a frequency of 1600 MHz.
Read everything about DDR2 and DDR3 RAM on the website
http://ru.wikipedia.org/wiki/DDR3 and everything will become clear to you.
Let's take another RAM module - Crucial 4GB DDR3 1333 (PC3 - 10600). This means the following: volume 4 GB, memory type DDR3, frequency 1333 MHz, PC3-10600 bandwidth is also indicated.
Manufacturer Patriot, capacity 1 GB, PC2 bandwidth – 6400. PC2 is a designation for peak bandwidth belonging only to the DDR2 type (for DDR3 RAM the designation will be PC3, for example PC3-12800). We divide the bandwidth of 6400 by eight and get 800. That is, this DDR2 memory stick operates at a frequency of 800 MHz.
One more plank- Kingston KHX6400D2 LL/1G
Manufacturer Kingston, bandwidth 6400, type DDR2, capacity 1 GB. We divide the bandwidth by 8, we get a frequency of 800 MHz.
But this stick of RAM has more important information, it has a non-standard microcircuit supply voltage: 2.0 V - set manually in the BIOS.
RAM modules differ in the size of the contact pads and the location of the cutouts. Using a cutout, you will not be able to install a RAM module in a slot not intended for it. For example, you cannot install a DDR3 memory stick in a DDR2 slot.
Everything is clearly visible in this diagram.
Sometimes there will be no clear information on the RAM module other than the name of the module itself. But the module cannot be removed, since it is under warranty. But by the name you can understand what kind of memory it is. For example
Kingston KHX1600 C9D3 X2K2/8G X, all this means:
KHX 1600 -> RAM operates at 1600 MHz
C9 -> Timings (Delays) 9-9-9
D3 -> RAM type DDR3
8G X -> Volume 4 GB.
You can simply type the name of the module in search engines and you will find out all the information about it.
For example, information from the AIDA64 program about my RAM. Kingston HyperX RAM modules are installed in RAM slots 2 and 4, memory type DDR3, frequency 1600 MHz
DIMM2: Kingston HyperX KHX1600C9D3/4GX DDR3-1600 DDR3 SDRAM
DIMM4: Kingston HyperX KHX1600C9D3/4GX DDR3-1600 DDR3 SDRAM
Is it possible to install RAM sticks with different frequencies into a computer?
The RAM frequency does not have to be the same. The motherboard will set the frequency for all installed RAM sticks according to the slowest module. But I want to say that often a computer with brackets of different frequencies is unstable.
Let's do a simple experiment. For example, let's take my computer, it has two identical Kingston HyperX RAM modules, memory type DDR3, frequency 1600 MHz.
If I run the AIDA64 program on my Windows 8, it will show the following information (see the following screenshot). That is, the program AIDA64 shows simple technical specifications each of the RAM sticks, in our case both sticks have a frequency1600 MHz. But the programAIDA64 does not show at what frequency the RAM modules are currently operating; this needs to be looked at in another program called CPU-Z.
If you run the free CPU-Z program and go to the Memory tab, it will show you exactly what frequency your RAM sticks are running at. My memory operates in dual-channel Dual mode, frequency 800 MHz, since the memory is DDR3, its effective (double) speed is 1600 MHz. This means that my RAM sticks operate exactly at the frequency for which they are designed: 1600 MHz. But what will happen if next to your RAM strips operating at a frequency 1600 MHz I will set another bar with frequency 1333 MHz!?
Let's install an additional DDR3 memory stick in my system unit, operating at a lower frequency of 1333 MHz.
Let's look at what AIDA64 shows, the program shows that an additional 4 GB stick is installed, with a frequency of 1333 MHz.
Now let’s run the CPU-Z program and see at what frequency all three sticks operate. As we can see, the frequency is 668.7 MHz, since the memory is DDR3, its effective (double) speed is 1333 MHz.
That is, the motherboard automatically set the operating frequency of all RAM sticks to the slowest module at 1333 MHz.
It is not advisable to install RAM sticks in your computer with a frequency higher than what the motherboard supports. For example, if your motherboard supports a maximum RAM frequency of 1600 MHz, and you installed a RAM module operating at a frequency of 1866 on your computer, then in the best case, this module will operate at a lower frequency of 1600 MHz, and in the worst case, the module will operate at its frequency 1866 MHz, but the computer will periodically reboot itself or you will get a blue screen when you boot the computer, in this case you will have to enter the BIOS and manually set the RAM frequency to 1600 MHz.
Timings(signal delay) determine how often the processor can access RAM. If you have a quad-core processor and it has a large second-level cache, then too long timings are not a problem, since the processor accesses RAM less often. Is it possible to install RAM sticks with different timings in a computer? The timings also do not have to match. The motherboard will automatically set timings for all modules according to the slowest module.
What conditions are needed for my memory to work in dual-channel mode? Before purchasing RAM, you need to study as much information as possible about the motherboard. All information about your motherboard can be found in the manual that came with it upon purchase. If the manual is lost, you need to go to the official website of your motherboard. You will also find the article “How to find out the model and all information about your motherboard” useful.Most often these days we find motherboards that support the RAM operating modes described below. Dual Mode (two-channel mode, most common)– if you look closely at the motherboard, you can see that the RAM slots are colored different colors. This was done on purpose and means that the motherboard supports dual-channel RAM mode. That is, two RAM modules with the same characteristics (frequency, timings) and the same volume are specially selected and installed in RAM slots of the same color.
If your computer has one stick of RAM installed, but the motherboard supports dual-channel mode, you can buy an additional stick of RAM of exactly the same frequency and capacity and install both sticks in DIMM slots of the same color.
Is there an advantage to dual channel mode over single channel mode?
During normal work on a computer, you will not notice the difference, but when working in applications that actively use RAM, such as Adobe Premiere Pro (video editing), (Canopus) ProCoder (video encoding), Photoshop (working with images), games, the difference can be feel.
Note: Some motherboards will operate in dual-channel mode even if you install RAM modules of different sizes in the same color DIMM slots. For example, you will install a 512MB module in the first DIMM slot, and a 1GB stick in the third slot. The motherboard activates dual-channel mode for the entire volume of the first 512MB stick, and for the second stick (interestingly) also 512MB, and the remaining 512MB of the second stick will work in single-channel mode.
How do I know if my RAM is working in dual channel mode or not? Download the free CPU-Z program and go to the Memory tab, look at the Channel parameter in our case - Dual, which means the RAM operates in dual-channel mode. If the Channels parameter is Single, then the RAM operates in single-channel mode.
My opinion is that during normal work on a computer they will work the same, I personally didn’t notice much of a difference. I worked for a long time on a computer with one large stick of RAM and the performance was the same as on exactly the same computer with two sticks of RAM running in dual-channel mode. A survey of friends and acquaintances of system administrators confirmed me in this opinion. But when working with programs that actively use RAM, for example Adobe Premiere Pro, Canopus ProCoder, Photoshop, games, a computer with two sticks of RAM will work faster.
Of course it is possible, but not advisable. The computer will work more stable if it implements the RAM operating mode recommended in the motherboard data sheet. For example, two-channel mode.
Nowadays the current RAM standard is DDR4, but many computers with DDR3, DDR2 and even DDR are still in use. Because of this type of RAM, many users get confused and forget which RAM is used on their computer. This article will be devoted to solving this problem. Here we will tell you how to find out what RAM is used on your computer: DDR, DDR2, DDR3 or DDR4.
If you have the opportunity to open the computer and inspect its components, then you can get all the necessary information from the sticker on the RAM module.
Usually on the sticker you can find an inscription with the name of the memory module. This name begins with the letters “PC” followed by numbers, and it indicates the type of RAM module in question and its bandwidth in megabytes per second (MB/s).
For example, if a memory module says PC1600 or PC-1600, then it is a first generation DDR module with a bandwidth of 1600 MB/s. If the module says PC2‑3200, then it is DDR2 with a bandwidth of 3200 MB/s. If PC3, then it is DDR3 and so on. In general, the first number after the letters PC indicates the DDR generation; if this number is not there, then it is a simple first generation DDR.
In some cases, RAM modules do not indicate the name of the module, but the type of RAM and its effective frequency. For example, the module may say DDR3 1600. This means that it is a DDR3 module with an effective memory frequency of 1600 MHz.
In order to correlate the names of modules with the type of RAM, and the bandwidth with the effective frequency, you can use the table that we provide below. The left side of this table shows the names of the modules, and the right side shows the type of RAM that corresponds to it.
| Module name | RAM type |
| PC-1600 | DDR-200 |
| PC-2100 | DDR-266 |
| PC-2400 | DDR-300 |
| PC-2700 | DDR-333 |
| PC-3200 | DDR-400 |
| PC-3500 | DDR-433 |
| PC-3700 | DDR-466 |
| PC-4000 | DDR-500 |
| PC-4200 | DDR-533 |
| PC-5600 | DDR-700 |
| PC2-3200 | DDR2-400 |
| PC2-4200 | DDR2-533 |
| PC2-5300 | DDR2-667 |
| PC2-5400 | DDR2-675 |
| PC2-5600 | DDR2-700 |
| PC2-5700 | DDR2-711 |
| PC2-6000 | DDR2-750 |
| PC2-6400 | DDR2-800 |
| PC2-7100 | DDR2-888 |
| PC2-7200 | DDR2-900 |
| PC2-8000 | DDR2-1000 |
| PC2-8500 | DDR2-1066 |
| PC2-9200 | DDR2-1150 |
| PC2-9600 | DDR2-1200 |
| PC3-6400 | DDR3-800 |
| PC3-8500 | DDR3-1066 |
| PC3-10600 | DDR3-1333 |
| PC3-12800 | DDR3-1600 |
| PC3-14900 | DDR3-1866 |
| PC3-17000 | DDR3-2133 |
| PC3-19200 | DDR3-2400 |
| PC4-12800 | DDR4-1600 |
| PC4-14900 | DDR4-1866 |
| PC4-17000 | DDR4-2133 |
| PC4-19200 | DDR4-2400 |
| PC4-21333 | DDR4-2666 |
| PC4-23466 | DDR4-2933 |
| PC4-25600 | DDR4-3200 |
In online stores, most often, RAM is designated using the memory type and effective frequency (for example, as DDR3-1333 or DDR4-2400), so if your memory has the name of the module written on it (for example, PC3-10600 or PC4-19200), then you can translate it using a table.
Using special programs
If your RAM modules are already installed in your computer, then you can find out what type they are using special programs.
The easiest option is to use free program CPU-Z To do this, launch CPU-Z on your computer and go to the “Memory” tab. Here, in the upper left corner of the window, the type of RAM that is used on your computer will be indicated. And just below is the total amount of RAM on your computer.
Also on the “Memory” tab you can find out the effective frequency at which your RAM operates. To do this, you need to take the value of the real clock frequency, which is indicated in the “DRAM Frequency” line, and multiply it by two. For example, in the screenshot below the frequency is 665.1 MHz, multiply it by 2 and get an effective frequency of 1330.2 MHz.
If you want to find out more detailed information about the RAM modules that are installed on your computer, you can do this on the “SPD” tab.
So we left Intel processors Haswell-E. The site has already tested the top 8-core Core i7-5960X, as well as the ASUS X99-DELUXE motherboard. And, perhaps, the main feature of the new platform is support for the DDR4 RAM standard.
The beginning of a new era, the DDR4 era
About the SDRAM standard and memory modules
The first SDRAM modules appeared back in 1993. They were released by Samsung. And by 2000, SDRAM memory, due to the production capacity of the Korean giant, had completely ousted the DRAM standard from the market.
The abbreviation SDRAM stands for Synchronous Dynamic Random Access Memory. This can be literally translated as “synchronous dynamic random access memory”. Let us explain the meaning of each characteristic. Memory is dynamic because, due to the small capacitor capacity, it constantly requires updating. By the way, in addition to dynamic memory, there is also static memory, which does not require constant data updating (SRAM). SRAM, for example, underlies cache memory. In addition to being dynamic, the memory is also synchronous, unlike asynchronous DRAM. Synchronicity means that the memory performs each operation for a known amount of time (or clock cycles). For example, when requesting any data, the memory controller knows exactly how long it will take for it to get there. The synchronicity property allows you to control the flow of data and queue it. Well, a few words about “random access memory” (RAM). This means that you can simultaneously access any cell at its address for reading or writing, and always at the same time, regardless of location.
SDRAM memory module
If we talk directly about the design of memory, then its cells are capacitors. If there is a charge in the capacitor, then the processor regards it as a logical unit. If there is no charge - as a logical zero. Such memory cells have a flat structure, and the address of each of them is defined as the row and column number of the table.
Each chip contains several independent memory arrays, which are tables. They are called banks. You can work with only one cell in a bank per unit of time, but it is possible to work with several banks at once. The information being recorded does not have to be stored in a single array. Often it is split into several parts and written to different banks, and the processor continues to consider this data as a single whole. This recording method is called interleaving. In theory, the more such banks in memory, the better. In practice, modules with a density of up to 64 Mbit have two banks. With a density of 64 Mbit to 1 Gbit - four, and with a density of 1 Gbit and higher - already eight.
What is a memory bank
And a few words about the structure of the memory module. The memory module itself is a printed circuit board with chips soldered on it. As a rule, you can find devices on sale made in the DIMM (Dual In-line Memory Module) or SO-DIMM (Small Outline Dual In-line Memory Module) form factors. The first is intended for use in full-fledged desktop computers, and the second is for installation in laptops. Despite the same form factor, memory modules of different generations differ in the number of contacts. For example, an SDRAM solution has 144 pins for connecting to the motherboard, DDR - 184, DDR2 - 214 pins, DDR3 - 240, and DDR4 - already 288 pieces. Of course, in this case we are talking about DIMM modules. Devices made in the SO-DIMM form factor naturally have a smaller number of contacts due to their smaller size. For example, a DDR4 SO-DIMM memory module is connected to the motherboard using 256 pins.
The DDR module (bottom) has more pins than SDRAM (top)
It is also quite obvious that the volume of each memory module is calculated as the sum of the capacities of each soldered chip. Memory chips, of course, can differ in their density (or, more simply, in volume). For example, last spring Samsung launched mass production of chips with a density of 4 Gbit. Moreover, in the foreseeable future it is planned to release memory with a density of 8 Gbit. Memory modules also have their own bus. The minimum bus width is 64 bits. This means that 8 bytes of information are transmitted per clock cycle. It should be noted that there are also 72-bit memory modules in which the “extra” 8 bits are reserved for ECC (Error Checking & Correction) error correction technology. By the way, the bus width of a memory module is also the sum of the bus widths of each individual memory chip. That is, if the memory module bus is 64-bit and there are eight chips soldered on the strip, then the memory bus width of each chip is 64/8 = 8 bits.
To calculate the theoretical bandwidth of a memory module, you can use the following formula: A*64/8=PS, where “A” is the data transfer rate, and “PS” is the required bandwidth. As an example, we can take a DDR3 memory module with a frequency of 2400 MHz. In this case, the throughput will be 2400*64/8=19200 MB/s. This is the number referred to in the marking of the PC3-19200 module.
How does information directly read from memory occur? First, the address signal is sent to the corresponding row (Row), and only then the information is read from the desired column (Column). The information is read into the so-called Sense Amplifiers - a mechanism for recharging capacitors. In most cases, the memory controller reads an entire packet of data (Burst) from each bit of the bus at once. Accordingly, when recording, every 64 bits (8 bytes) are divided into several parts. By the way, there is such a thing as data packet length (Burst Length). If this length is 8, then 8*64=512 bits are transmitted at once.
Memory modules and chips also have such a characteristic as geometry, or organization (Memory Organization). The module geometry shows its width and depth. For example, a chip with a density of 512 Mbit and a bit depth (width) of 4 has a chip depth of 512/4 = 128M. In turn, 128M=32M*4 banks. 32M is a matrix containing 16000 rows and 2000 columns. It can store 32 Mbit of data. As for the memory module itself, its width is almost always 64 bits. The depth is easily calculated using the following formula: the volume of the module is multiplied by 8 to convert from bytes to bits, and then divided by the bit depth.
You can easily find the timing values on the markings
It is necessary to say a few words about such characteristics of memory modules as timings. At the very beginning of the article, we said that the SDRAM standard provides for such a point that the memory controller always knows how long a particular operation takes to complete. Timings precisely indicate the time required to execute a certain command. This time is measured in memory bus clocks. The shorter this time, the better. The most important delays are:
- TRCD (RAS to CAS Delay) - the time required to activate the bank line. Minimum time between activation command and read/write command;
- CL (CAS Latency) - time between issuing a read command and the start of data transfer;
- TRAS (Active to Precharge) - line activity time. The minimum time between activating a line and the command to close the line;
- TRP (Row Precharge) - time required to close a row;
- TRC (Row Cycle time, Activate to Activate/Refresh time) - time between activation of rows of the same bank;
- TRPD (Active bank A to Active bank B) - time between activation commands for different banks;
- TWR (Write Recovery time) - time between the end of writing and the command to close the bank line;
- TWTR (Internal Write to Read Command Delay) - time between the end of the write and the read command.
Of course, these are not all the delays that exist in memory modules. You can list a dozen more different timings, but only the above parameters significantly affect memory performance. By the way, only four delays are indicated in the labeling of memory modules. For example, with parameters 11-13-13-31, the CL timing is 11, TRCD and TRP are 13, and TRAS is 31 clock cycles.
Over time, the potential of SDRAM reached its ceiling, and manufacturers were faced with the problem of increasing the performance of RAM. This is how the DDR.1 standard was born
The Coming of DDR
The development of the DDR (Double Data Rate) standard began back in 1996 and ended with the official presentation in June 2000. With the advent of DDR, SDRAM memory became a thing of the past and was simply called SDR. How does the DDR standard differ from SDR?
Once all SDR resources were exhausted, memory manufacturers had several options to solve the problem of improving performance. It would be possible to simply increase the number of memory chips, thereby increasing the capacity of the entire module. However, this would have a negative impact on the cost of such solutions - this idea was very expensive. Therefore, the JEDEC manufacturers association took a different route. It was decided to double the bus inside the chip, and also transmit data at twice the frequency. In addition, DDR provided for the transmission of information on both edges of the clock signal, that is, twice per clock. This is where the abbreviation DDR - Double Data Rate - comes from.
Kingston DDR Memory Module
With the advent of the DDR standard, such concepts as real and effective memory frequency appeared. For example, many DDR memory modules ran at 200 MHz. This frequency is called real. But due to the fact that data transfer was carried out on both edges of the clock signal, manufacturers, for marketing purposes, multiplied this figure by 2 and obtained a supposedly effective frequency of 400 MHz, which was indicated in the labeling (in this case, DDR-400). At the same time, the JEDEC specifications indicate that using the term “megahertz” to characterize the level of memory performance is completely incorrect! Instead, "millions of transfers per second per data output" should be used. However, marketing is a serious matter, and few people were interested in the recommendations specified in the JEDEC standard. Therefore, the new term never took root.
Also in the DDR standard, a dual-channel memory mode appeared for the first time. It could be used if there was an even number of memory modules in the system. Its essence is to create a virtual 128-bit bus by interleaving modules. In this case, 256 bits were sampled at once. On paper, a dual-channel mode can double the performance of the memory subsystem, but in practice the speed increase is minimal and is not always noticeable. It depends not only on the RAM model, but also on timings, chipset, memory controller and frequency.
Four memory modules operate in dual-channel mode
Another innovation in DDR was the presence of a QDS signal. It is located on the printed circuit board along with the data lines. QDS was useful when using two or more memory modules. In this case, the data arrives at the memory controller with a slight time difference due to the different distances to them. This creates problems when choosing a clock signal for reading data, which QDS successfully solves.
As mentioned above, DDR memory modules were made in DIMM and SO-DIMM form factors. In the case of DIMMs, the number of pins was 184 pieces. In order for DDR and SDRAM modules to be physically incompatible, the key for DDR solutions (the cut in the pad area) was located in a different location. In addition, DDR memory modules operated at a voltage of 2.5 V, while SDRAM devices used a voltage of 3.3 V. Accordingly, DDR had lower power consumption and heat dissipation compared to its predecessor. The maximum frequency of DDR modules was 350 MHz (DDR-700), although JEDEC specifications only provided for a frequency of 200 MHz (DDR-400).
DDR2 and DDR3 memory
The first DDR2 modules went on sale in the second quarter of 2003. Compared to DDR, second-generation RAM has not received significant changes. DDR2 used the same 2n-prefetch architecture. If previously the internal data bus was twice as large as the external one, now it has become four times wider. At the same time, the increased performance of the chip began to be transmitted via an external bus at double the frequency. Precisely frequency, but not double transmission speed. As a result, we found that if the DDR-400 chip operated at a real frequency of 200 MHz, then in the case of DDR2-400 it operated at a speed of 100 MHz, but with twice the internal bus.
Also, DDR2 modules received a larger number of contacts for connection to the motherboard, and the key was moved to another location for physical incompatibility with SDRAM and DDR sticks. Has been reduced again operating voltage. While DDR modules operated at a voltage of 2.5 V, DDR2 solutions operated at a potential difference of 1.8 V.
By by and large, this is where all the differences between DDR2 and DDR end. At first, DDR2 modules were characterized by high latencies, which made them inferior in performance to DDR modules with the same frequency. However, the situation soon returned to normal: manufacturers reduced latencies and released faster sets of RAM. The maximum DDR2 frequency reached an effective 1300 MHz.
Different key positions for DDR, DDR2 and DDR3 modules
The transition from DDR2 to DDR3 followed the same approach as the transition from DDR to DDR2. Of course, data transmission at both ends of the clock signal has been preserved, and the theoretical throughput has doubled. DDR3 modules retained the 2n-prefetch architecture and received 8-bit prefetch (DDR2 had 4-bit). At the same time, the internal tire became eight times larger than the external one. Because of this, once again, with the change of memory generations, its timings increased. The nominal operating voltage for DDR3 has been reduced to 1.5 V, making the modules more energy efficient. Note that, in addition to DDR3, there is DDR3L memory (the letter L means Low), which operates with a voltage reduced to 1.35 V. It is also worth noting that DDR3 modules turned out to be neither physically nor electrically compatible with any of the previous generations of memory.
Of course, DDR3 chips have received support for some new technologies: for example, automatic signal calibration and dynamic signal termination. However, in general, all changes are predominantly quantitative.
DDR4 - another evolution
Finally, we get to the completely new DDR4 memory. The JEDEC Association began developing the standard back in 2005, but only in the spring of this year the first devices went on sale. As stated in a JEDEC press release, during development, engineers tried to achieve the highest performance and reliability, while increasing the energy efficiency of the new modules. Well, we hear this every time. Let's see what specific changes DDR4 memory has received in comparison with DDR3.
In this picture you can trace the evolution of DDR technology: how the voltage, frequency and capacitance indicators changed
One of the first DDR4 prototypes. Oddly enough, these are laptop modules
As an example, consider an 8GB DDR4 chip with a 4-bit wide data bus. Such a device contains 4 groups of banks, 4 banks each. Inside each bank there are 131,072 (2 17) rows with a capacity of 512 bytes each. For comparison, you can give the characteristics of a similar DDR3 solution. This chip contains 8 independent banks. Each bank contains 65,536 (2 16) rows, and each row contains 2048 bytes. As you can see, the length of each line of a DDR4 chip is four times less than the length of a DDR3 line. This means that DDR4 scans banks faster than DDR3. At the same time, switching between the banks themselves also occurs much faster. Let us immediately note that for each group of banks there is an independent choice of operations (activation, read, write or regeneration), which allows increasing the efficiency and memory bandwidth.
The main advantages of DDR4: low power consumption, high frequency, large capacity of memory modules
Here once again I was asked how to appearance you can determine the type of RAM. Because This question comes up periodically, I decided that it was better to show it once than to explain it a hundred times, and write an illustrated mini-review of types of RAM for PCs.
Not everyone is interested in this, that’s why I’m hiding it under the cat. Read
The most common types of RAM that have been and are used in personal computers commonly called SIMM, DIMM, DDR, DDR2, DDR3. You are unlikely to see SIMMs and DIMMs anymore, but DDR, DDR2 or DDR3 are now installed in most personal computers. So, in order
SIMM
SIMM for 30 contacts. Used in personal computers with processors from 286 to 486. Now it is already a rarity. 
SIMM for 72 contacts. This type of memory was of two types: FPM (Fast Page Mode) and EDO (Extended Data Out).
The FPM type was used on computers with 486 processors and the first Pentiums until 1995. Then EDO appeared. Unlike its predecessors, EDO begins fetching the next block of memory at the same time it sends the previous block to the CPU.
Structurally they are identical, they can only be distinguished by markings. Personal computers that supported EDO could also work with FPM, but the opposite was not always the case.
DIMM
This is the name given to the memory type SDRAM (Synchronous DRAM). Starting in 1996, most Intel chipsets began to support this type of memory module, making it very popular until 2001. Most computers with Pentium and Celeron processors used this type of memory.
DDR
DDR (Double Data Rate) was a development of SDRAM. This type of memory module first appeared on the market in 2001. The main difference between DDR and SDRAM is that instead of doubling the clock speed to speed things up, these modules transfer data twice per clock cycle.
DDR2
DDR2 (Double Data Rate 2) is a newer variant of DDR that should theoretically be twice as fast. DDR2 memory first appeared in 2003, and chipsets supporting it appeared in mid-2004. The main difference between DDR2 and DDR is the ability to operate at a significantly higher clock frequency, thanks to improvements in design. In appearance it differs from DDR in the number of contacts: it has increased from 184 (for DDR) to 240 (for DDR2).
DDR3
Like DDR2 memory modules, they are produced in the form of a 240-pin printed circuit board (120 pins on each side of the module), but are not electrically compatible with the latter, and for this reason have a different “key” arrangement. 
And finally, there is another type of RAM - RIMM (Rambus). Appeared on the market in 1999. It is based on traditional DRAM, but with a radically changed architecture. This type of RAM did not take root in personal computers and was used very rarely. Such modules were also used in the Sony Playstation 2 and Nintendo 64 game consoles.
SIMM for 30 contacts.
RAM modules on modern computers can be presented in a variety of modifications. Among the most common are DDR2 and DIMM. What are they?
Facts about DDR2
DDR2 is a type of RAM for PCs and computer video cards, which has a main bus that operates at approximately twice the frequency of that installed in the previous generation of RAM modules - DDR. The design of DDR2 RAM chips has 240 pins.
DDR2 modules are available in 5 main modifications, differing in frequency (from 100 MHz, which is the least productive version, to 266 MHz, which is set for the fastest types of DDR2 RAM).
DDR2 RAM can be supplemented with:
- special error correction chips;
- modules for additional registration of cell addresses;
- chips for data buffering.
DDR2 modules are characterized by very high bandwidth, low power consumption, and efficient design (from the point of view of the cooling system). However, in some cases, accessing data in DDR2 modules operating at high frequencies may occur with a delay that exceeds that in previous generation microcircuits.
DIMM Facts
DIMM, in turn, is not a type of RAM, but a form factor of the corresponding modules. That is, in essence, a design concept that is followed by manufacturers of RAM chips in order to achieve mutual compatibility of their products. Brands that supply DDR2 memory modules to the market are no exception. Modifications of RAM chips such as DDR3 and DDR4 also comply with the DIMM standard.
RAM modules, made in the DIMM form factor, are rectangular chips with contacts on both sides that are independent of each other. In turn, the contacts on the RAM, corresponding to the historically previous DIMM form factor - SIMM, are interconnected.
DIMMs are ideally suited for installation in 64-bit computers. In fact, many IT specialists associate the development and distribution of this form factor with the growing popularity of 64-bit PCs. However, historically, DIMM memory modules have been used for quite a long time - since the early 90s. Then they were installed on workstations.
Comparison
The main difference between DDR2 and DIMM is that DDR2 is a technological type of RAM modules, and DIMM is a form factor. At the same time, DDR2 in modern modifications in most cases is made precisely in the DIMM standard. In turn, not every DIMM form factor is available in DDR2 - as we noted above, DIMM RAM modules have been used since the early 90s, when RAM in the DDR2 modification had not even been brought to the market yet. Perhaps they weren’t even invented.
Having determined what the difference is between DDR2 and DIMM, let’s note its key criteria in a small table.
