Maximum frequency supported by ddr 1. History of DDR4 development. Features of DDR3L RAM

What kind of standard is DDR3? Memory Synchronous Dynamic Random Access Memory, third generation of Double Data Rate standard- simply DDR3 SDRAM, is a new generation of DDR memory, replacing the current generation of DDR2 SDRAM. Modern architecture dynamic memory DRAM has crossed the stages of single and double speed data transfer, and now, at the DDR3 stage, we can talk about per-pin peak performance of up to 1.6 Gbps per signal pin for DDR3 (100 Mbps per pin for SDRAM). While maintaining the basic structure of the architecture, key changes were made to the prefetch circuits and the design of the I/O buses. To put it simply, in the case of DDR3, each read or write operation means access to eight groups of data (words) of DDR3 DRAM, which, in turn, are multiplexed across the I/O pins using two different reference oscillators at four times the clock frequency .

Among the main advantages of the new standard, first of all, it is worth noting lower power consumption, approximately 40% than that of popular DDR2 modules. The main reason for saving energy consumption is the use of a new generation of DDR3 memory chips, which are produced by most manufacturers in compliance with the 90 nm process technology. This allows you to reduce the operating voltages of the chips - up to 1.5 V for DDR3, which is lower than 1.8 V for DDR2 or 2.5 V for DDR; plus, further reduce operating currents by using dual-gate transistors to reduce leakage currents. In practice, this will lead to the fact that, for example, DDR3-1066 modules, which significantly exceed the performance of DDR2-800 modules and consume 15% less in sleep mode, will have energy consumption comparable to DDR2-667 modules. Does the new DDR3 RAM have anything to do with the GDDR3 graphics memory in video cards or Xbox 360 consoles? No, it doesn't. Similar names hide different architectures, with completely different buffering schemes, etc. So from now on it is better not to confuse the terms “DDR3” and “GDDR3”. What are the main functional features of DDR3 memory? The main features of the DDR3 SDRAM chip architecture are as follows:

Appearance of asynchronous reset contact (RESET)
Support System Level Flight Time Compensation
"Mirror" pinout of chips with convenient pin placement for assembling a DIMM module (On-DIMM Mirror friendly DRAM ballout)
The emergence of a high-speed buffer CWL (CAS Write Latency)
On-chip I/O calibration module
READ and WRITE calibration
Typical (expected) chip markings depending on speed: DDR3-800, DDR3-1066, DDR3-1333, DDR3-1600

Main features of DDR3 modules:

"Network" Fly-by topology of command/address/control bus with on-module (On-DIMM) termination
Precision external resistors (ZQ resistors) in calibration circuits

Will DDR3 be faster than DDR2, what are the pros and cons of these types of memory? The performance of DDR3 memory modules in the future should significantly exceed the capabilities of the current generation of DDR2 memory - if only because theoretically effective DDR3 frequencies will be located in the range of 800 MHz - 1600 MHz (at clock frequencies of 400 MHz - 800 MHz). While for DDR2 the effective operating frequencies are 400 MHz - 1066 MHz (clock frequencies 200 MHz - 533 MHz), and for DDR - even 200 MHz - 600 MHz (100 MHz - 300 MHz). In addition, DDR3 memory has an 8-bit prefetch buffer, while the current DDR2 memory has a 4-bit one, and DDR had a 2-bit one. The prefetch buffer, it should be noted, is a fairly important element of modern memory modules, since it is responsible for caching data before it is required. Thus, the 8-bit DDR3 prefetch allows us to talk about the operation of the module’s I/O buses at a clock frequency 8 times higher than the clock frequency. The second reason for the increase in DDR3 performance can be safely called the new dynamic on-chip termination circuitry (Dynamic On-Die Termination), which is calibrated during the initialization process to achieve optimal interaction between the memory and the system. Finally, unlike DDR2, where termination was only partially applied, DDR3 memory has full termination, including addresses and commands. The advantages of DDR3 over DDR2 include higher clock speeds - up to 1600 MHz, increased performance with lower power consumption (respectively, longer battery life for laptops), as well as improved thermal design. The disadvantage of DDR3 versus DDR2 is higher latency. Who develops, promotes and intends to support DDR3 memory? All leading IT industry companies that are members of the standard-setting committee for DDR3 under the JEDEC (Joint Electronic Device Engineering Council) took part in the development and approval of the DDR3 standard. Currently, more than 270 companies are participating in the DDR3 section, including Intel, AMD, Samsung, Qimonda, Micron, Corsair, OCZ and others. Why did the effective “market life” of DDR2 memory turn out to be so short compared to DDR, and does DDR3 memory face the same short fate? In fact, we must remember that at the dawn of the development of DDR technology, as they say, there was no “unity among comrades” among manufacturers of processors and chipsets. Veterans of the IT market will easily remember the “standards wars” that were raging at that time, for which the Rambus company and its RDRAM rightly deserved the lion’s share of “gratitude.” Because of this, initially good DDR memory is sufficient for a long time marked time and for more than five years it clock frequency grew to only 500 MHz, and DDR2 managed to go from DDR2-533 to DDR2-1066 in just three years - which, by the way, is a typical lifespan for a memory architecture.

Alas, at the current stage, the DDR2 architecture is actually starting to hit the ceiling of its capabilities, which is tied to processor clock speeds and bus topology. It's too early to talk about the lifespan of DDR3, but it wouldn't be incredible if in three years it's replaced by something like DDR4. That is life. So what is the “ceiling” of clock frequencies of DDR3 DIMM memory modules? So far we are talking about DDR3-1600 chips, on the basis of which PC3-12800 modules with a bandwidth of up to 12.80 Gb/s will be produced. However, Intel documentation has already mentioned that DDR3 can theoretically be scaled to frequencies up to 2133 MHz. Is there a physical difference between DDR2 and DDR3 modules? DDR3 DIMM memory modules for desktop PCs will have a 240-pin structure, familiar to us from DDR2 modules; however, there will be no physical compatibility due to different DIMM key locations. This “foolproof protection”, which prevents the installation of DDR3 modules in boards for DDR2 and vice versa, is provided not only due to pin-to-pin incompatibility of the modules, but also due to different supply voltages and signal levels of different generations random access memory. What types of DDR3 modules will be typical in the memory market? DDR3 memory modules are expected to be available in Registered DIMM, Unbuffered DIMM, FB-DIMM, SO-DIMM, Micro-DIMM and 16-bit/32-bit SO-DIMM variants. Regarding DDR3 memory form factors - which is critical for the server market, we can say that 1.2-inch (30 mm) modules for 1U servers, typical for the industry since 1999, will be presented, as well as VLP modules with a height of 18.3 mm for Blade servers, 38 mm modules for 2U servers and even “higher” modules. What will be the typical capacity of DDR3 DIMMs? Even at the testing stage of the DDR3 standard, manufacturers worked with chips with a capacity of 512 Mbit and created 1 GB modules; theoretically, the capacity of DDR3 modules can reach 8 Gbit. The typical capacity of DDR3 DIMM memory modules as their popularity grows will be 1 GB - 4 GB, theoretically - up to 32 GB. As for DDR3 SO-DIMMs for mobile PCs, samples of which are expected to appear soon, and mass production (at least by Samsung) is planned for early 2008, typical capacities will be in the range of 512 MB - 4 GB. The first DDR3 DIMMs will certainly not be cheap. How soon are prices for DDR3 DIMM memory modules expected to drop to normal “mass” levels? It is expected that already in 2007, memory module manufacturers will make an aggressive start in the DDR3 market, and, as the new generation platforms become established and become more widespread, memory will become cheaper. According to preliminary forecasts from Intel, DDR3 memory will become widespread this year, and in 2008 we can talk about its widespread use - at least, iSuppli's forecasts confirm this. There is a DDR3 standard, there will be boards soon, but will manufacturers with DDR3 chips and DIMM modules be in time for the announcement? Undoubtedly. The industry as a whole is ready for the advent of DDR3; many chip and memory manufacturers have already announced that their products have been validated by Intel and are ready for mass production.

The full line of chips that have gone through Intel's testing, qualification and validation process can be viewed on this page:

Validated DDR3 800/1066MHz SDRAM Components

Module manufacturers also announced full readiness. Thus, Corsair has already presented 1 GB DDR3-1066 DHX modules with 6-6-6-24 timings, and for the future, the DOMINATOR series is preparing to release DDR3-1333 and higher modules this quarter. OCZ Technology recently presented its sets of PC3-8500 modules (1066 MHz, CL 7-7-7-21) in the Gold Series (with gold-plated XTC heatsinks), in 2 x 512 MB (OCZ3G10661GK) and 2 x 1 GB versions (OCZ3G10662GK), as well as sets of PC3-10666 modules (1333 MHz, CL 9-9-9-26) of the same series in 2 x 512 MB (OCZ3G13331GK) and 2 x 1 GB (OCZ3G13332GK) versions. What number of DDR3 DIMM slots will be typical for new systems?

Initially, the idea of using high-capacity 1 Gbit and 2 Gbit chips was aimed at reducing the number of slots on the board to two without having to sacrifice the amount of supported memory. However, the typical buyer still prefers to upgrade, especially while memory is not cheap. This is why a typical motherboard will still have four DDR3 DIMM slots.

When will DDR3 support be released by AMD?

AMD, among other leaders in the computer industry, has announced support and plans to switch to DDR3 memory, but only in the distant future. AMD is conducting research in the field of DDR3 support in close cooperation with SimpleTech. It is already reliably known that the integrated memory controllers of AMD processors with the working title Barcelona will support DDR2-1066 modules. DDR2-1066 modules are currently undergoing a standardization procedure in the JEDEC organization, and AMD plans to delay the transition to DDR3 by extending the life of DDR2. Remember, the same situation arose during the transition to DDR2, then AMD also could not say goodbye to DDR for quite a long time. It is expected that for the first time DDR3 memory will be supported by AMD processors for the AM3 socket, and such chips will be shown no earlier than the third quarter of 2008. Now AMD experts call the transition to widespread use of DDR3 memory in desktop systems premature - they say, we will wait for 2009, when this type of memory will become quite widespread and relatively inexpensive. Although, there is already information that testing and validation of chips by AMD, which began in 2007, will “take off” already in 2008. Well, Intel The role of the “industry locomotive” in pushing new standards is again proposed. On the other hand, one cannot help but admit that this position, by offering truly advanced technologies and productive solutions, regularly helps it, as they say, “skim off the cream.” So what about AMD? Alas, the new processor core with the working title Griffin, the appearance of which can be expected in early 2008, will also only have a built-in DDR2 memory controller - albeit an advanced, dual one, with two independent operating modes, but, nevertheless, without the slightest hint of DDR3 support. Since the production cycle of AMD processors generally fits within an 18-month cycle, it will approximately turn out that AMD chips will acquire DDR3 support no earlier than 2009, or even later. What chipsets with DDR3 support can we expect from Intel in the near future? What and when is expected in retail? Of course, among the first motherboards with DDR3 support, we should expect new products based on the new generation Intel 3 Series chipsets - those that were collectively working title Intel Bearlake. These chipsets will support new processors Intel Core with FSB 1333 MHz and new DDR3-1333 RAM. However, it’s worth mentioning right away that not every chipset out of the seven expected in the Bearlake series - X38, P35, G35, G33, G31, Q35 and Q31, will work with DDR3 (as well as with the new FSB 1333 MHz processors) - traditionally, We are talking only about chipsets for the High-end and Mainstream markets.

Full official information about Intel 3 Series Bearlake chipsets will appear on our website soon enough. For FAQ articles for DDR3, we have prepared a special “lightweight” table, clarifying support for RAM standards.

Intel 3 Series (Bearlake) chipset specifications, DDR3 support

Chipset		X38	P35	G35	G33	G31	Q35	Q33
Working title		Bearlake X	Bearlake P	Broadwater	Bearlake G	Bearlake GZ	Bearlake Q	Bearlake QF
Approximate announcement date		3rd quarter	June	3rd quarter	June	3rd quarter
Market segment		Enthusiasts, gamers	Mainstream			Value	Business Mainstream	Business Value
CPU support	Core2 Extreme
	Core2 Quad
	Core2 Duo
	Yorkdale
	Wolfdale
FSB	1333 MHz
	1066 MHz
	800 MHz
Memory	Slots	4 (2 DIMM x 2 channels)
	Max. capacity
	Support	DDR3/DDR2			DDR3/DDR2
FSB combined with memory	1333/DDR3-1333
	1333/DDR3-1066
	1333/DDR3-800
	1066/DDR3-1066
	1066/DDR3-800
	800/DDR3-800
	1333/DDR2-800
	1333/DDR2-667
	1066/DDR2-800
	1066/DDR2-667
	800/DDR2-800
	800/DDR2-667
Integrated Graphics	Int. core			4th generation	3.5 generation
	DirectX			DX10
	Codec VC-1
	External video	PCIe 2x16 (5 Gb/s)	PCIe x16
South Bridge	ICH9
	ICH9R
	ICH9DO
	ICH9DH
	ICH8
	ICH8R
	ICH8DH
	ICH7
	ICH7DH
Technologies	PCI Express 2.0
	AMT 3.0
	VT-D
	TXT (LaGrande)
Platform	VPro
Platform	Viiv

As you can see from the table, the first chipsets with DDR3 support - P35 and G33, will be presented very soon, in June, with an eye to delivering the first boards in June-July. Of course, the first motherboards based on these chipsets in retail versions will be shown during the June Computex 2007 exhibition in Taipei, but to say now how many manufacturers will risk starting shipping their new products with DDR3 support is still a big question. However, we can already say for sure that a number of companies are preparing for production of motherboards supporting both DDR3 and DDR2. Top X38 chipset with two PCI slots Express x16, which will replace the flagship Intel 975X, will have to wait until the fall. When will DDR3 support be released? mobile platforms oh Intel? The Intel mobile platform, codenamed Santa Rosa, which is expected to appear in the second half of 2007, will work exclusively with DDR2 memory, this is embedded in the architecture of the Intel Mobile 965 Express chipsets. The same can be said about the updated version of the Santa Rosa platform with the working title "Santa Rosa+", changes in which will be associated mainly with new mobile processors of the Penryn architecture. Another thing is the new generation of Intel's mobile platform with the working title Montevina, which is expected to be presented in a year, closer to the summer of 2008. According to preliminary data, the Montevina platform will have a completely updated design of 45 nm mobile processors with Penryn architecture. In particular, the lineup chipsets for the Montevina platform codenamed Cantiga with a TDP of about 15 W will be equipped southern bridges ICH9M, Shiloh (Wi-Fi) or Echo Peak (Wi-Fi/WiMAX) wireless modules, Boaz LAN module. Integrated versions of the Cantiga chipsets will feature 457 MHz Gen 4.5 integrated graphics (essentially an improved version of the upcoming Calistoga chipset with Gen 4 GMA X3100 graphics).

However, for us in today’s material the most interesting thing is that Cantiga chipsets will support FSB 1066 MHz, as well as SO-DIMM memory modules of DDR2-667 (DDR2-800 will not be supported) and DDR3-800 standards. Alas, in the mobile version - starting only with DDR3-800, but this is already good in terms of efficiency and performance. There is no information yet about the longer-term prospects of DDR3 for mobile platforms. Should we expect chipsets for motherboards with DDR3 support from other manufacturers in the near future? Speaking about DDR3 chipsets, it’s worth mentioning right away that for now we can only talk about supporting platforms with Intel processors. The reason is clear: until they appear AMD processors with an integrated DDR3 memory controller, there is nothing to talk about. The SiS company promises the availability of working samples of the first proprietary chipsets with DDR3 support and built-in DX10 Mirage 4 graphics in the near future. The new chipsets, according to preliminary information, will be called SiS673 and SiS673 FX. The SiS673 chipset will support Intel processors with a 1066 MHz FSB and 2-channel DDR2-800/DDR3-1066 memory, while the more powerful SiS673 FX chipset will be able to support DDR2-1066/DDR3-1333 and processors with a 1333 MHz FSB. Mass production of SiS673 may begin in the third quarter of 2007. First discrete north bridge SiS665 will be introduced towards the end of 2007. The start of mass production of SiS665 is now positioned for 2008. It is assumed that UMC will produce the chipset using an 80 nm process technology. Most likely, SiS665 will support two standards at once: DDR2 and DDR3. According to the company's plans, SiS665 will support the PCI Express 2.0 bus. For the mobile solutions market, SiS plans to introduce IGP chipsets with support for DirectX 10 and DDR3 memory. The SiS M673 chipset will support the “old” Pentium 4 NetBurst, M673MX – Pentium M processors, both will work with DDR3 and DDR2 with operating frequencies of 533/667 MHz. Both chipsets - SiS M673 and SiS M673MX, will work with SiS 968/969 southbridges. VIA Technology plans to introduce PM960 and PT960 chipsets that support Intel processors with 1333 MHz FSB, DDR3 memory and new interface PCI Express 2.0. The integrated version - VIA PM960, with the new graphics core S3 Chrome 9 HD (450 MHz), will become the main version for Vista Premium Ready PCs. The PT960 discrete northbridge will support single-channel DDR2-1066/DDR3-1333 memory. We hope this post will help you understand the new DDR3 RAM standard. We will be glad to receive your comments, criticism, corrections and additions to this collection of questions and answers. If there is no answer to your question among the published ones, write, the FAQ will be constantly supplemented and improved.

Double Data Rate Synchronous Dynamic Random Access Memory - synchronous dynamic memory with random access and double data transfer rate) - a type of computer memory used in computing as RAM and video memory. It replaced SDRAM type memory.

When using DDR SDRAM, twice the operating speed is achieved than in SDRAM, due to reading commands and data not only on the edge, as in SDRAM, but also on the fall of the clock signal. This doubles the data transfer rate without increasing the memory bus clock frequency. Thus, when DDR operates at 100 MHz, we will get an effective frequency of 200 MHz (when compared with the SDR SDRAM analogue). The JEDEC specification makes a note that it is incorrect to use the term “MHz” in DDR; the correct rate is “millions of transfers per second per data pin.”

The specific operating mode of memory modules is dual-channel mode.

Description

DDR SDRAM memory chips are produced in TSOP packages and (later mastered) BGA (FBGA) packages, manufactured according to 0.13 and 0.09-micron process standards:

IC supply voltage: 2.6 V +/- 0.1 V
Power consumption: 527 mW
I/O Interface: SSTL_2

The memory bus width is 64 bits, that is, 8 bytes are simultaneously transferred along the bus in one clock cycle. As a result, we obtain the following formula for calculation maximum speed transfers for of this type memory: ( memory bus clock speed)x 2 (data transfer twice per clock) x 8 (number of bytes transmitted per clock cycle). For example, to ensure data transfer twice per clock cycle, a special “2n Prefetch” architecture is used. The internal data bus is twice as wide as the external one. When transmitting data, the first half of the data bus is transmitted first on the rising edge of the clock signal, and then the second half of the data bus on the falling edge.

In addition to double data transfer, DDR SDRAM has several other fundamental differences from simple SDRAM. Basically, they are technological. For example, a QDS signal has been added and is located on the PCB along with the data lines. It is used for synchronization during data transfer. If two memory modules are used, then the data from them arrives at the memory controller with a slight difference due to different distances. A problem arises in choosing a clock signal for reading them, and the use of QDS successfully solves this.

JEDEC sets standards for DDR SDRAM speeds, divided into two parts: the first for memory chips, and the second for memory modules, which, in fact, house the memory chips.

Memory chips

Each DDR SDRAM module contains several identical DDR SDRAM chips. For modules without error correction (ECC) their number is a multiple of 4, for modules with ECC the formula is 4+1.

Memory chip specification

DDR200: DDR SDRAM type memory operating at 100 MHz
DDR266: DDR SDRAM type memory operating at 133 MHz
DDR333: DDR SDRAM type memory operating at 166 MHz
DDR400: DDR SDRAM type memory operating at 200 MHz

Chip characteristics

Chip capacity ( DRAM density). Recorded in megabits, for example, 256 Mbit - a chip with a capacity of 32 megabytes.
Organization ( DRAM organization). It is written as 64M x 4, where 64M is the number of elementary storage cells (64 million), and x4 (pronounced “by four”) is the bit capacity of the chip, that is, the bit capacity of each cell. DDR chips come in x4 and x8, the latter are cheaper per megabyte of capacity, but do not allow the use of Chipkill, memory scrubbing and Intel SDDC functions.

Memory modules

DDR SDRAM modules are made in the DIMM form factor. Each module contains several identical memory chips and an SPD configuration chip. Registered memory modules also contain register chips that buffer and amplify the signal on the bus; non-registered memory modules do not have them.

Module characteristics

Volume. Specified in megabytes or gigabytes.
Number of chips ( # of DRAM Devices). A multiple of 8 for modules without ECC, a multiple of 9 for modules with ECC. Chips can be located on one or both sides of the module. The maximum number that fits on a DIMM is 36 (9x4).
Number of rows (ranks) ( # of DRAM rows (ranks)).

The chips, as can be seen from their characteristics, have a 4- or 8-bit data bus. To provide higher bandwidth (e.g. DIMM requires 64 bits and 72 bits for ECC memory), chips are linked into ranks. The memory rank has a common address bus and complementary data lines. One module can accommodate several ranks. But if necessary more memory, then you can continue to add ranks by installing several modules on one board and using the same principle: all ranks sit on the same bus, only the select chips are different - each has its own. A large number of ranks electrically loads the bus, more precisely the controller and memory chips, and slows down their operation. Hence, they began to use multi-channel architecture, which also allows independent access to several modules.

Delays (timings): CAS Latency (CL), Clock Cycle Time (tCK), Row Cycle Time (tRC), Refresh Row Cycle Time (tRFC), Row Active Time (tRAS).

The characteristics of the modules and the chips they consist of are related.

The volume of the module is equal to the product of the volume of one chip and the number of chips. When using ECC, this number is further multiplied by a factor of 9/8, since there is one bit of error control redundancy per byte. Thus, the same memory module volume can be dialed a large number(36) small chips or a small number (9) larger chips.

The total capacity of the module is equal to the product of the capacity of one chip by the number of chips and is equal to the product of the number of ranks by 64 (72) bits. Thus, increasing the number of chips or using x8 chips instead of x4 leads to an increase in the number of module ranks.

IN in this example possible module layouts are compared server memory volume 1 GB. Of the presented options, you should prefer the first or third, since they use x4 chips that support advanced error correction and failure protection methods. If you need to use peer-to-peer memory, only the third option remains available, but depending on the current cost of 256 Mbit and 512 Mbit chips, it may turn out to be more expensive than the first.

Memory module specification

Memory module specification

Specification	Memory bus clock speed	Maximum Theoretical Memory Bandwidth
Specification	Memory bus clock speed	in single channel mode	in two-channel mode
PC1600* (DDR200)	100 MHz	1600 MB/sec	3200 MB/sec
PC2100* (DDR266)	133 MHz	2133 MB/sec	4267 MB/sec
PC2400 (DDR300)	150 MHz	2400 MB/sec	4800 MB/sec
PC2700* (DDR333)	166 MHz	2667 MB/sec	5333 MB/sec
PC3200* (DDR400)	200 MHz	3200 MB/sec	6400 MB/sec
PC3500 (DDR433)	217 MHz	3467 MB/sec	6933 MB/sec
PC3700 (DDR466)	233 MHz	3733 MB/sec	7467 MB/sec
PC4000 (DDR500)	250 MHz	4000 MB/sec	8000 MB/sec
PC4200 (DDR533)	267 MHz	4267 MB/sec	8533 MB/sec

Note 1: standards marked with an “*” are officially certified by JEDEC. The remaining types of memory are not JEDEC certified, although many memory manufacturers produced them, and most recently released motherboards supported these types of memory.

Note 2: memory modules were produced that operated at higher frequencies (up to 350 MHz, DDR700), but these modules were not used in great demand and were produced in small quantities, in addition, they had a high price.

Module sizes are also standardized by JEDEC.

It should be noted that there is no difference in the architecture of DDR SDRAM with different frequencies, for example, between PC1600 (operating at 100 MHz) and PC2100 (operating at 133 MHz). The standard simply says at what guaranteed frequency this module operates.

DDR SDRAM memory modules can be distinguished from regular SDRAM by the number of pins (184 pins for DDR modules versus 168 pins for modules with regular SDRAM) and by the key (cutouts in the pad area) - SDRAM has two, DDR has one. According to JEDEC, DDR400 modules operate at a supply voltage of 2.6 V, and all slower modules operate at a voltage of 2.5 V. Some high-speed modules operate at higher voltages, up to 2.9 V, to achieve high frequencies.

Most of the latest chipsets with DDR support allowed the use of DDR SDRAM modules in dual-channel mode, and some chipsets in quad-channel mode. This method allows you to increase the theoretical bandwidth of the memory bus by 2 or 4 times, respectively. For memory to operate in dual-channel mode, 2 (or 4) memory modules are required; it is recommended to use modules operating at the same frequency and having the same capacity and timings (even better to use absolutely identical modules).

Now DDR modules have been practically replaced by modules of the DDR2 and DDR3 types, which, as a result of some changes in the architecture, make it possible to obtain greater bandwidth of the memory subsystem. Previously, the main competitor of DDR SDRAM was RDRAM memory (Rambus), but due to the presence of some shortcomings, over time it was practically forced out of the market.

Notes

Literature

V. Solomenchuk, P. Solomenchuk PC hardware. - 2008. - ISBN 978-5-94157-711-8

Guk M. Yu. IBM PC hardware. Encyclopedia. - Peter, 2006. - 1072 p.

Kopeikin M. V., Spiridonov V. V., Shumova E. O. Organization of computers and systems. (Computer memory): Textbook. Benefit. - St. Petersburg, 20064. - 153 p.

Links

Description and illustration of almost all DDR memory parameters (Russian)
Intel® Server Board SE7501CW2 Memory List Test Report Summary (PDF, 246,834 bytes) (English) - a small list of possible memory module configurations.
Kingston's Literature Page - several reference documents describing the organization of memory modules.

Types of Dynamic Random Access Memory (DRAM)
Asynchronous	FPM RAM · EDO RAM
Synchronous

RAM is a special chip used to store data of all kinds. There are many varieties of these devices, they are produced by various companies. The best manufacturers Most often they are of Japanese origin.

What is it and what is it for?

RAM (so-called RAM memory) is a type of volatile chip used to store all kinds of information. Most often it contains:

machine code of programs currently running (or in standby mode);
input and output data.

Photo: RAM from different manufacturers

Data exchange between the central processor and RAM is carried out in two ways:

using ultra-fast register ALU;
through a special cache (if included in the design);
directly (directly via the data bus).

The devices in question are circuits built on semiconductors. All information stored in all kinds of electronic components remains accessible only in the presence of electric current. As soon as the voltage is completely turned off, or a short-term power failure occurs, then everything contained inside the RAM is erased or destroyed.

An alternative is ROM type devices.

Types and amount of memory Today the board can have a capacity of several tens of gigabytes. Modern technical means

allow you to use it as quickly as possible. Most operating systems are equipped with the ability to interact with such devices. There is a proportional relationship between the amount of RAM and the cost. The larger its size, the more expensive it is. And vice versa. Also, the devices in question may have different frequencies.

The value of this characteristic also directly affects the cost of the device in question. The current fastest modification can “remember” 128 GB. It is produced by a company called Hynix and has the following performance characteristics:

All modern RAM can be divided into two types:

static;
dynamic.

Static type

More expensive today is the static microcircuit. It is labeled as SDRAM. Dynamic is cheaper.

Distinctive features of the SDRAM variety are:

Another distinctive feature of RAM is the ability to select the bit into which any information will be written.

The disadvantages include:

low recording density;
relatively high cost.

Computer RAM devices of all kinds (SDRAM and DRAM) have external differences. They consist in the length of the contact part. Its shape also differs. The designation of RAM is located both on the sticker label and printed directly on the bar itself.

Today there are many different modifications of SDRAM. It is designated as:

DDR 2;
DDR 3;
DDR4.

Dynamic type

Another type of microcircuit is referred to as DRAM. It is also completely volatile, with write bits being accessed randomly. This type is widely used in most modern PCs. It is also used in those computer systems, where latency requirements are high, the performance of DRAM is an order of magnitude higher than SDRAM.

DRAM - dynamic memory

Most often, this type has the form factor DIMM type. The same design solution is used to manufacture a static circuit (SDRAM). A feature of the DIMM version is that there are contacts on both sides of the surface.

OP parameters

The main criteria for choosing microcircuits of this type are their operating parameters.

You should primarily focus on the following points:

frequency of operation;
timings;
voltage.

They all depend on the type specific model. For example, DDR 2 will perform various actions clearly faster than the DDR 1 bar, since it has more outstanding performance characteristics.

Timings are the time delays for information between various components devices. There are quite a few types of timings, all of them directly affect performance. Small timings allow you to increase execution speed various operations. There is one unpleasant proportional relationship - the higher the speed of the random access memory device, the greater the timings.

The way out of this situation is to increase the operating voltage - the higher it is, the shorter the timings become. The number of operations performed per unit of time increases at the same time.

Frequency and speed

The higher the RAM bandwidth, the faster its speed. Frequency is a parameter that determines the bandwidth of the channels through which various types of data are transmitted to the CPU through the motherboard.

It is advisable that this characteristic coincided with the permissible operating speed motherboard.

For example, if the bracket supports a frequency of 1600 MHz, and the motherboard supports no more than 1066 MHz, then the speed of data exchange between the RAM and the CPU will be limited precisely by the capabilities of the motherboard. That is, the speed will be no more than 1066 MHz.

Performance

Performance depends on many factors. The number of strips used has a very large influence on this parameter. Dual-channel RAM works an order of magnitude faster than single-channel RAM. The ability to support multi-channel modes is indicated on a sticker located on top of the board.

These designations are as follows:

To determine which mode is optimal for a particular motherboard, you need to count the total number of connection slots and divide them by two. For example, if there are 4 of them, then you need 2 identical strips from the same manufacturer. With them parallel installation Dual mode is activated.

Working principle and functions

The operation of the OP is implemented quite simply; writing or reading data is carried out as follows:

Each column is connected to an extremely sensitive amplifier. It records the flow of electrons that occurs when the capacitor is discharged. In this case, the corresponding command is given. Thus, access to various cells located on the board occurs. There is one important nuance that you should definitely know. When an electrical impulse is applied to any line, it opens all its transistors. They are connected to it directly.

From this we can conclude that one line is the minimum amount of information that can be read when accessing. The main purpose of RAM is to store various types of temporary data that are necessary while the personal computer is turned on and the operating system is functioning.

The most important executable files are loaded into RAM, and the CPU executes them directly, simply storing the results of the operations performed.

Photo: interaction of memory with processor

The cells also store:
executable libraries;
key codes that were pressed;

results of various mathematical operations. If necessary, everything that is in RAM CPU can save on HDD

. And do it in the form in which it is necessary.

Manufacturers You can find it in stores great amount

RAM from a wide variety of manufacturers. A large number of such products began to be supplied from Chinese companies.

Today, the most productive and high-quality products are the following brands:
Kingston;
Hynix;
Corsair;
Kingmax.

Samsung.

It is a compromise between quality and performance.

Table of RAM characteristics

RAM of the same type from different manufacturers has similar performance characteristics.

That is why it is correct to carry out comparisons taking into account only the type:

Performance and price comparison

The performance of RAM directly depends on its cost. You can find out how much a DDR3 module costs at your nearest computer store; you should also check out the price of DDR 1. By comparing their operating parameters and price, and then testing them, you can easily verify this. It is most correct to compare RAM of the same type, but with different performance

, depending on the frequency of operation:	Type	Operating frequency, MHz	Cost, rub.Speedwork, Aida 64,
Memory Read, MB/s	1333	3190	19501
Memory Read, MB/s	1600	3590	22436
Memory Read, MB/s	1866	4134	26384
Memory Read, MB/s	2133	4570	30242
Memory Read, MB/s	2400	6548	33813
Memory Read, MB/s	2666	8234	31012
Memory Read, MB/s	2933	9550	28930

DDR 3

In Aida 64, all DDR 3 tests were performed on identical hardware:
OS: Windows 8.1;
CPU: i5-4670K;
video card: GeForce GTX 780 Ti;

motherboard: LGA1150, Intel Z87. RAM is a very important part of a PC, greatly affecting its performance. That is why, to increase it, it is recommended to install strips with high frequency

and small timings. This will give a big boost to your computer's performance; it is especially important for games and various professional programs.

RAM modules are made on the basis of rectangular printed circuit boards with single-sided or double-sided arrangement of chips. 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 vertically into the motherboard connector and secured 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 - buffer memory and error control chip; 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.

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, listening to music, etc.), 1024 MB of memory (1 GB) will be enough for you. For demanding computer games, video processing, sound recording and mixing of musical compositions at home - at least 2 GB (2048 MB) of RAM. Preferably 3 gigabytes. It should also be noted that 32-bit versions (x86) of Windows do not support more than 3 gigabytes of RAM. We also note that 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 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 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 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 most sure signs existence of memory problems.

Periodic malfunctions and 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). Note.

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.

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

Inside each connector there are small jumper keys, and on the contact part of the memory modules there are corresponding cutouts. Their mutual alignment eliminates 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).