What is ddr in motherboard?
Double Data Rate Synchronous Dynamic Random-Access Memory (DDR SDRAM) is a double data rate (DDR) synchronous dynamic random-access memory (SDRAM) class of memory integrated circuits used in computers. DDR SDRAM, also retroactively called DDR1 SDRAM, has been superseded by DDR2 SDRAM, DDR3 SDRAM, DDR4 SDRAM and DDR5 SDRAM. None of its successors are forward or backward compatible with DDR1 SDRAM, meaning DDR2, DDR3, DDR4 and DDR5 memory modules will not work in DDR1-equipped motherboards, and vice versa.
Compared to single data rate (SDR) SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals. Implementations often have to use schemes such as phase-locked loops and self-calibration to reach the required timing accuracy. The interface uses double pumping (transferring data on both the rising and falling edges of the clock signal) to double data bus bandwidth without a corresponding increase in clock frequency. One advantage of keeping the clock frequency down is that it reduces the signal integrity requirements on the circuit board connecting the memory to the controller. The name "double data rate" refers to the fact that a DDR SDRAM with a certain clock frequency achieves nearly twice the bandwidth of a SDR SDRAM running at the same clock frequency, due to this double pumping.
With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate (in bytes/s) of (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.
In the late 1980s IBM had built DRAMs using a dual-edge clocking feature and presented their results in the International Solid-State Circuits Convention in 1990.
Samsung demonstrated the first DDR memory prototype in 1997, and released the first commercial DDR SDRAM chip (64 Mbit) in June 1998, followed soon after by Hyundai Electronics (now SK Hynix) the same year. The development of DDR began in 1996, before its specification was finalized by JEDEC in June 2000 (JESD79). JEDEC has set standards for data rates of DDR SDRAM, divided into two parts. The first specification is for memory chips, and the second is for memory modules. The first retail PC motherboard using DDR SDRAM was released in August 2000.
To increase memory capacity and bandwidth, chips are combined on a module. For instance, the 64-bit data bus for DIMM requires eight 8-bit chips, addressed in parallel. Multiple chips with the common address lines are called a memory rank. The term was introduced to avoid confusion with chip internal rows and banks. A memory module may bear more than one rank. The term sides would also be confusing because it incorrectly suggests the physical placement of chips on the module. All ranks are connected to the same memory bus (address + data). The chip select signal is used to issue commands to specific rank.
Adding modules to the single memory bus creates additional electrical load on its drivers. To mitigate the resulting bus signaling rate drop and overcome the memory bottleneck, new chipsets employ the multi-channel architecture.
Note: All above listed are specified by JEDEC as JESD79F. All RAM data rates in-between or above these listed specifications are not standardized by JEDEC – often they are simply manufacturer optimizations using tighter tolerance or overvolted chips. The package sizes in which DDR SDRAM is manufactured are also standardized by JEDEC.
There is no architectural difference between DDR SDRAM modules. Modules are instead designed to run at different clock frequencies: for example, a PC-1600 module is designed to run at 100 MHz, and a PC-2100 is designed to run at 133 MHz. A module's clock speed designates the data rate at which it is guaranteed to perform, hence it is guaranteed to run at lower (underclocking) and can possibly run at higher (overclocking) clock rates than those for which it was made.
DDR SDRAM modules for desktop computers, dual in-line memory modules (DIMMs), have 184 pins (as opposed to 168 pins on SDRAM, or 240 pins on DDR2 SDRAM), and can be differentiated from SDRAM DIMMs by the number of notches (DDR SDRAM has one, SDRAM has two). DDR SDRAM for notebook computers, SO-DIMMs, have 200 pins, which is the same number of pins as DDR2 SO-DIMMs. These two specifications are notched very similarly and care must be taken during insertion if unsure of a correct match. Most DDR SDRAM operates at a voltage of 2.5 V, compared to 3.3 V for SDRAM. This can significantly reduce power consumption. Chips and modules with DDR-400/PC-3200 standard have a nominal voltage of 2.6 V.
JEDEC Standard No. 21–C defines three possible operating voltages for 184 pin DDR, as identified by the key notch position relative to its centreline. Page 4.5.10-7 defines 2.5V (left), 1.8V (centre), TBD (right), while page 4.20.5–40 nominates 3.3V for the right notch position. The orientation of the module for determining the key notch position is with 52 contact positions to the left and 40 contact positions to the right.
Increasing operating voltage slightly can increase maximum speed, at the cost of higher power dissipation and heating, and at the risk of malfunctioning or damage.
Module and chip characteristics are inherently linked.
Total module capacity is a product of one chip's capacity and the number of chips. ECC modules multiply it by 8⁄9 because they use 1 bit per byte (8 bits) for error correction. A module of any particular size can therefore be assembled either from 32 small chips (36 for ECC memory), or 16(18) or 8(9) bigger ones.
DDR memory bus width per channel is 64 bits (72 for ECC memory). Total module bit width is a product of bits per chip and number of chips. It also equals number of ranks (rows) multiplied by DDR memory bus width. Consequently, a module with a greater number of chips or using ×8 chips instead of ×4 will have more ranks.
This example compares different real-world server memory modules with a common size of 1 GB. One should definitely be careful buying 1 GB memory modules, because all these variations can be sold under one price position without stating whether they are ×4 or ×8, single- or dual-ranked.
There is a common belief that number of module ranks equals number of sides. As above data shows, this is not true. One can also find 2-side/1-rank modules. One can even think of a 1-side/2-rank memory module having 16(18) chips on single side ×8 each, but it is unlikely such a module was ever produced.
From Ballot JCB-99-70, and modified by numerous other Board Ballots, formulated under the cognizance of Committee JC-42.3 on DRAM Parametrics.
Standard No. 79 Revision Log:
"This comprehensive standard defines all required aspects of 64Mb through 1Gb DDR SDRAMs with X4/X8/X16 data interfaces, including features, functionality, ac and dc parametrics, packages and pin assignments. This scope will subsequently be expanded to formally apply to x32 devices, and higher density devices as well."
PC3200 is DDR SDRAM designed to operate at 200 MHz using DDR-400 chips with a bandwidth of 3,200 MB/s. Because PC3200 memory transfers data on both the rising and falling clock edges, its effective clock rate is 400 MHz.
1 GB PC3200 non-ECC modules are usually made with 16 512 Mbit chips, 8 on each side (512 Mbits × 16 chips) / (8 bits (per byte)) = 1,024 MB. The individual chips making up a 1 GB memory module are usually organized as 226 8-bit words, commonly expressed as 64M×8. Memory manufactured in this way is low-density RAM and is usually compatible with any motherboard specifying PC3200 DDR-400 memory.
DDR (DDR1) was superseded by DDR2 SDRAM, which had modifications for higher clock frequency and again doubled throughput, but operates on the same principle as DDR. Competing with DDR2 was Rambus XDR DRAM. DDR2 dominated due to cost and support factors. DDR2 was in turn superseded by DDR3 SDRAM, which offered higher performance for increased bus speeds and new features. DDR3 has been superseded by DDR4 SDRAM, which was first produced in 2011 and whose standards were still in flux (2012) with significant architectural changes.
DDR's prefetch buffer depth is 2 (bits), while DDR2 uses 4. Although the effective clock rates of DDR2 are higher than DDR, the overall performance was not greater in the early implementations, primarily due to the high latencies of the first DDR2 modules. DDR2 started to be effective by the end of 2004, as modules with lower latencies became available.
Memory manufacturers stated that it was impractical to mass produce DDR1 memory with effective transfer rates in excess of 400 MHz (i.e. 400 MT/s and 200 MHz external clock) due to internal speed limitations. DDR2 picks up where DDR1 leaves off, utilizing internal clock rates similar to DDR1, but is available at effective transfer rates of 400 MHz and higher. DDR3 advances extended the ability to preserve internal clock rates while providing higher effective transfer rates by again doubling the prefetch depth.
The DDR4 SDRAM is a high-speed dynamic random-access memory internally configured as 16 banks, 4 bank groups with 4 banks for each bank group for ×4/×8 and 8 banks, 2 bank groups with 4 banks for each bank group for ×16 DRAM. The DDR4 SDRAM uses an 8n prefetch architecture to achieve high-speed operation. The 8n prefetch architecture is combined with an interface designed to transfer two data words per clock cycle at the I/O pins. A single read or write operation for the DDR4 SDRAM consists of a single 8n-bit-wide 4-clock data transfer at the internal DRAM core and 8 corresponding n-bit-wide half-clock-cycle data transfers at the I/O pins.
RDRAM was a particularly expensive alternative to DDR SDRAM, and most manufacturers dropped its support from their chipsets. DDR1 memory's prices substantially increased from Q2 2008, while DDR2 prices declined. In January 2009, 1 GB DDR1 was 2–3 times more expensive than 1 GB DDR2.
MDDR is an acronym that some enterprises use for Mobile DDR SDRAM, a type of memory used in some portable electronic devices, like mobile phones, handhelds, and digital audio players. Through techniques including reduced voltage supply and advanced refresh options, Mobile DDR can achieve greater power efficiency.
When it comes to picking out RAM, though, things can get a little confusing. How many individual modules should you use? What’s the difference between DDR 3 RAM and DDR 4 RAM? Can different types of RAM be mixed together?
In this article, we’ll provide a newbie-friendly primer on RAM, explain the different DDR speeds, and outline which types of RAM are best for PC gaming.
The RAM you use for a gaming PC is called SDRAM, or Synchronous Dynamic Random-Access Memory. SDRAM is also divided into a number of speed classes using the Double Data Rate (or DDR) classing system. There’s also a second type of RAM called Graphics DDR (or GDDR) RAM which is designed for graphics cards, but for the scope of this article we’ll just focus on DDR SDRAM for motherboards.
Each module of DDR SDRAM is produced as a sort of long stick with memory chips fused onto the sides. Along the bottom of each RAM stick is a series of pins, and those pins are meant to match the DIMM (Dual Inline Memory Module) slots on your computer’s motherboard. Typically, most motherboards have a total of four DIMM slots, though some have more or less than that.
The amount of memory on a single RAM stick can vary, with higher capacity sticks being more expensive. Most non-gaming computers have between 2-4GB of RAM, but for high-end gaming you’ll definitely want at least 8GB, and preferably 12-16GB if you’re able. Just know that more RAM means more strain on your computer’s power supply and CPU so make sure your other components can handle the load.
For more on how much RAM you need for your system, check out our guide:
RAM is pretty easy to install into your computer’s motherboard as long as you’re doing it correctly. The pins on the bottom of each RAM stick are notched, which means the RAM modules can only be inserted into the DIMM slot one way. Also, if you’re using two RAM modules at once, you want to make sure they’re inserted into matching DIMM slots on your motherboard (these slots are usually color-coded and oftentimes not right next to each other).
Lastly, you should make sure your RAM’s DDR type (more on that in a moment) is compatible with your motherboard (not all motherboards accept all DDR types). Most modern motherboards only support DDR4 as of this writing, but some still support DDR3. It’s important to check your motherboard’s documentation and make absolutely sure that your motherboard supports the type of RAM you’re considering.
As we mentioned above, DDR stands for Double Data Rate. This is a natural evolution of the now obsolete SDR (Single Data Rate) SDRAM, and over the years the base DDR version has been surpassed by DDR2, DDR3, and DDR4 SDRAM (with DDR5 set to arrive in the next year or so).
As of this writing, DDR4 SDRAM is considered to be the baseline standard in PC gaming. However, you can get away with using DDR3 if you want to save a little money and/or you’re not building a super high-end rig.
Each increasing DDR class outperforms its predecessor when it comes to elements like clock speed, performance, bus speed, and throughput. In fact, DDR and DDR2 SDRAM are virtually obsolete as of this writing (most modern motherboards only support DDR4, though you can still find plenty of DDR3-compatible models). In terms of performance DDR4 does offer a boost over DDR3 (though it might not always be something you actually notice in games), and it has become commonplace enough that you’re usually better off going with DDR4 just for the sake of future-proofing your system.
If you want to dive into the technical weeds a bit, here’s a chart outlining the differences between standard SDR SDRAM, DDR, DDR2, DDR3, and DDR4.
If you’re picking between DDR 3 and DDR4 RAM, the only issue you have to consider is cost vs. performance. As we mentioned above, you likely won’t notice a huge difference between DDR3 and DDR4 RAM unless you’re playing the newest games at ultra settings on a high-end PC. However, DDR4 has almost completely eclipsed DDR3 when it comes to retail availability. Unless you’re really trying to save money, you’re usually better off going with DDR4 just to give yourself less of a shopping hassle.
As for RAM, you may think the more is the better. Although much RAM means that your system can run well, the amount of the RAM isn’t the only factor you need to consider when you purchase a memory module. The data transfer speed and type of RAM can also affect efficiency.
When it comes to the memory type, DRAM memory and SRAM memory are two common types of RAM. Among them, DRAM, short for dynamic random-access memory, is the most common type of PC RAM and is widely used. It can be used for data or program code required by a computer processor to run.
Double Data Rate SDRAM, also known as DDR SDRAM, is a type of DRAM memory. It has different iterations, including DDR2 SDRAM, DDR3 SDRAM, and DDR4 SDRAM. When reading here, you may ask: how do I know what DDR my RAM is? Now, you can get the answer from the following part.
Knowing what kind of RAM you have is very simple and you can follow these two ways below.
How to check what RAM I have via Task Manager? You may ask. The steps are easy and just follow the guide.
Step 1: Launch Task Manager by right-clicking the toolbar on the bottom of the computer screen and choose Task Manager.
Step 2: Go to the Performance tab, click Memory and you can know how many GB of the RAM, the speed (1600MHz), slots, form factor. Besides, you can know what DDR your RAM is. From the following screenshot, we know the type is DDR3.
In addition to using Task Manager, you can use a professional RAM checker tool for PC to check RAM type. CPU-Z is such a tool. And you can free download and use it in Windows 10.
Want to know the answer to the question “how to check what RAM I have”? Follow these steps below.
Step 1: Go to download CPU-Z via the link.
Step 2: After finishing installing this tool, launch it, and go to the Memory tab to get the detailed RAM specifications of your PC. CPU-Z lists your RAM type like DDR3. Besides, its size, NB frequency, number of operating channels, DRAM frequency, and more information are also displayed.
What does DDR stand for? DDR stands for Double Data Rate . DDR transfers data to the processor on both the rising and falling edges of the clock signal, so twice per cycle.
