Technology Explained

What’s the Difference Between DDR2, DDR3, and DDR4 RAM?

Ben Stegner Updated 07-10-2019

RAM, which stands for Random Access Memory, is a short-term storage location your computer uses for running processes. You might not think much about RAM besides the amount of it when buying a new computer.


But not all RAM is created equal. Different generations of RAM provide different speeds and are only compatible with certain systems. Here are the differences between DDR2 and DDR3 RAM, compared to the newer DDR4 RAM.

What Is DDR RAM?

If you’re new to RAM, you might not know what “DDR” means. This abbreviation stands for double data rate.

In simple terms, operating at a double data rate means the RAM can transfer data two times per clock cycle. As you probably know, all data on a computer is digital, meaning it’s represented by a 1 (on) or a 0 (off).

One clock cycle is represented by the CPU signal going from off to on and back again. This is usually measured from the halfway point, as you can see in the chart below.

DDR Clock Cycle
Image credit: MisterSanderson/Wikimedia Commons


This double data rate is a major upgrade from old SDR (single data rate) RAM, which only operated once per clock cycle. Original DDR RAM first became generally available in 2000, and like SDR RAM, is now obsolete. Virtually all RAM you’ll find available now is some generation of DDR.

But why do these generations of RAM change?

DDR Generations Explained

Original DDR RAM was superseded by DDR2, DDR3, and now DDR4. These are all future generations of the same technology with faster speed and other improvements, and are all the same physical size.

This isn’t out of the ordinary, since many computing standards evolve over time. But you might wonder where DDR2 and DDR3 came from, and why they emerged.


The generation of RAM used with a computer is closely tied to the development of processors and motherboards. As companies like Intel come out with new CPU technology, they require new motherboard chipsets. This is a set of electronic components that let all the parts of a computer communicate properly.

New generations of RAM are necessary to work with the latest chipsets. This is why we’ve seen DDR2, DDR3, and DDR4 RAM after the original generation. Without these advancements, we wouldn’t be able to put RAM into newer systems.

Importantly, RAM is not backwards or forwards-compatible. If your motherboard is designed for DDR4 RAM, DDR3 RAM simply won’t work in it. It’s thus vital when building or upgrading a PC that you buy the right generation of RAM for compatibility.

Each generation of RAM has its notch in a slightly different position, so it’s impossible to put the wrong type in your computer.


RAM Generations Chart


8gb ddr4 2133 ram crucial

You might wonder how the newer generations of DDR RAM stack up. Let’s look at DDR2 and DDR3 RAM differences first. While you’re unlikely to find DDR2 RAM in many places today (it did become available back in 2004) it’s still useful for comparison.

While original-generation DDR RAM ran two data transfers per clock cycle, DDR2 RAM can produce four transfers per cycle instead. DDR3 takes this even further, as it can produce eight transfers for every clock cycle.


When it comes to speed, DDR3 is unsurprisingly faster. One way to measure RAM speed is megatransfers per second, or MT/s. This refers to the number of operations the RAM can complete every second; 1MT/s is one million transfers per second.

While DDR2 RAM has data transfer rates ranging from 400 to 1,066MT/s, DDR3 smashes this at 800-2,133MT/s.

Voltage is another important aspect of RAM generations. DDR2 RAM uses 1.8V, while DDR3 is lower at 1.5V. Lower voltage means the RAM uses less power, thus putting less strain on the CPU.

You can find sticks of DDR2 RAM that are 4GB, but the most common maximum is 2GB. Practically, DDR3 RAM caps out at 8GB per stick, though some 16GB sticks are available.


Continuing with our discussion of RAM differences, how does DDR4 RAM stack up? DDR3 was introduced in 2007 and while it’s still used with some older systems today, DDR4 has become the standard.

DDR4 runs at an even lower voltage than DDR3, at just 1.2V. It’s also capable of more operations per second, ranging from 1,600MT/s to 3,200MT/s.

Samsung sells a single 32GB stick of DDR4 RAM, but it’s quite expensive. The maximum you’ll see in the wild is usually 16GB.

If you’re in the market, we have a buying guide covering the best DDR4 RAM The Best DDR4 RAM to Improve Your PC's Performance If your computer is feeling sluggish or slow, then you may be due a RAM upgrade. Here's the best DDR4 RAM for your next upgrade. Read More .

Coming Soon: DDR5 RAM

At the time of writing, DDR4 RAM is the standard. But DDR5 is on the horizon, expected to launch sometime in 2020.

It will probably be a few years before DDR5 becomes standard, so you’re fine to build a computer with DDR4 RAM now.

How RAM Differences Affect You

We’ve thrown around a lot of values above, but don’t feel overwhelmed. The average user shouldn’t ever have to worry about which generation of RAM to buy. You can simply let the motherboard/processor you want to purchase dictate what RAM to get. When building a computer today, you’ll almost certainly have a setup that uses DDR4 RAM.

You might wonder how the different RAM generations affect performance. For the average user, it really won’t make much of a difference. DDR4 is theoretically faster than DDR3, but it’s not often that RAM speed is the bottleneck on your system.

In most cases, other upgrades will improve your computer’s performance more Which Upgrades Will Improve Your PC Performance the Most? Need a faster computer but aren't sure what you should upgrade on your PC? Follow our PC upgrade checklist to find out. Read More . Swapping an old HDD for an SSD, adding more overall RAM, or upgrading your processor will have a much greater effect than slightly faster RAM.

The main scenario where the intricacies of RAM really matter is in heavy use, such as in servers. These machines run heavy loads constantly, meaning that every bit of performance is vital. In normal use, you’d be hard-pressed to feel a difference between two systems with identical stats except for the generation of RAM.

Other Important Aspects of RAM

If you buy a prebuilt computer off the shelf, everything is already assembled, so there’s no worry. But if you’re building your own PC, you should be aware of other RAM values aside from the generation that we’ve focused on here.

Have a look at our general guide to RAM A Quick and Dirty Guide to RAM: What You Need to Know RAM is a crucial component of every computer, but it can be confusing. We break it down in easy-to-grasp terms you'll understand. Read More , which goes into more detail on other specifications.

DDR vs. DDR2 vs. DDR3 vs. DDR4: Cleared Up

Now you know the basic differences between DDR2 and DDR3, plus what DDR4 brings to the table.

In essence, DDR2, DDR3, and the rest are incremental improvements on the same technology. Aside from making sure you purchase RAM that’s compatible with your system (ideally the newest generation), you don’t need to worry much about it. But it’s useful to know what all those numbers and letters mean for RAM.

If you’re a PC gamer, dive deeper into this topic with our guide to RAM for gaming What Does RAM Do for Gaming and How Much RAM Do I Need? Wondering how RAM affects your gaming PC and what kind of RAM you should buy? Here's an explanation of RAM for gamers. Read More .

Related topics: Computer Memory, Hardware Tips.

Affiliate Disclosure: By buying the products we recommend, you help keep the site alive. Read more.

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  1. skyeler
    October 30, 2018 at 8:49 am

    ehh seems like an overreaction, long as your not trying to use the newest software you'll be fine iv got a DDR2 system that runs just fine if not better then my older DDR3 system 50% of everyone's problem when they have an obsolete system is they expect it to run fine without a tuneup... when you have a older system you gotta push it that extra mile if you expect it to compete with any newer requirements overclocking your CPU and GPU can do a hell of a lot for performance if you don't really give a crap about burning out your hardware a little earlier, and so many times i run into gamers running games at full performance on a mediocre system wondering why they are lagging... its like turn your bloody performance settings down to low and maybe you might have less laggy gameplay, not saying my rig couldn't be faster but its not like im expecting anything fantastic out of outdated hardware i just expect it to run it also helps that my ram is a set of 4 dual channel sticks and if your using an ATA drive as your master drive there's your problem entirely only ever use ATA as storage space and consider buying at-least a SATA drive you'll notice a world of difference in speed

  2. Zack
    November 16, 2016 at 7:48 pm

    I have a HP Z800 Workstation. Does that mean, that most of my programs on my PC won't be able to use all the ram, or am I not getting it?


  3. Roshan
    May 31, 2016 at 4:00 pm

    It is very helpful. Thank you very much.

  4. Bearlikestrong
    April 21, 2016 at 6:00 pm

    Very helpful. Thanks!

  5. shekhar
    February 4, 2016 at 2:51 am

    can u tell me where ROM is located on motherboard?

    • jaden
      February 25, 2016 at 3:34 am

      rom is your hard drive

      • Dalibor Fencl
        August 26, 2016 at 9:05 am

        No it is not. Hard drive is an hard drive. ROM is ROM. Usually only BIOS/bootstrap firmware is installed in ROM, so it is just small chip hidden somewhere on the motherboard. You dont need to take any care of it.

        • kataa
          December 5, 2018 at 7:11 am

          ROM is your hard drive. EEPROM is where your bios is stored.

  6. Anonymous
    October 1, 2015 at 5:52 pm

    very nice thank you

  7. M.S. Smith
    October 10, 2010 at 7:22 pm

    ACard already makes these [Broken Link Removed]

  8. Lehcyfer
    October 10, 2010 at 2:16 pm

    If DDR2 will be dirt cheap in a short while, then maybe someone can make a project of solid state RAM disc with, lets say 32 sticks inside giving 64 GB of fast external memory - perhaps with some sort of battery powered memory support, making it perfect for fast system disc...

    • M.S. Smith
      October 10, 2010 at 5:22 pm

      ACard already makes these

      [Broken Link Removed]

  9. Delaorden
    September 11, 2010 at 2:18 pm

    HEy man, I'm from a place where people still handles DDR (1) so I wouldn't take any offense in case you send your sparing sticks of DDR2. I'll be waiting for your reply and send you further details.Please, send it by express courier. Appreciate

  10. Doc
    September 11, 2010 at 5:57 am

    "The typical enthusiast won’t see much benefit from memory with a higher clock speed." Wrong, only the enthusiasts will see the benefits. Typical users won't see that much (word processing, spreadsheet, web surfing...)

  11. Doc
    September 11, 2010 at 3:57 am

    "The typical enthusiast won’t see much benefit from memory with a higher clock speed." Wrong, only the enthusiasts will see the benefits. Typical users won't see that much (word processing, spreadsheet, web surfing...)

  12. Mpdnnrd
    September 11, 2010 at 3:16 am

    Does this also relate to memory used in graphics cards? I noticed that a lot of the upper end cards are now using DDR5. So how does this compare to DDR2/3 and should this matter when matching memory for SLI systems?

    • M.S. Smith
      September 13, 2010 at 2:04 am

      No, it doesn't. Two cards with different kinds of memory should work together just fine - proved that those two types of cards aren't limited by some other conflict. Using mis-matched graphics cards in SLI/CrossFire is often tricky business.

  13. Ari
    September 10, 2010 at 8:16 pm

    There is something called as RAM timings, u could have included that also.

    • M.S. Smith
      September 11, 2010 at 12:13 am

      This is true. RAM timing is a fairly subtle part of RAM, however. I was more aiming to get people who aren't clear on the DDR2 vs. DDR3 issue up to speed.

  14. Josh Gunderson
    September 10, 2010 at 7:00 pm

    "I have four sticks of spare DDR2 memory that are no longer capable of finding a home in a new system"
    I can probably find a home for those. ;)

  15. Josh Gunderson
    September 10, 2010 at 5:00 pm

    "I have four sticks of spare DDR2 memory that are no longer capable of finding a home in a new system"
    I can probably find a home for those. ;)

  16. Philippe
    September 10, 2010 at 6:12 pm

    Their is not much performance difference between the two according to this review :

    DDR2 is not that obselete in my opinion.

  17. Philippe
    September 10, 2010 at 4:12 pm

    Their is not much performance difference between the two according to this review :

    DDR2 is not that obselete in my opinion.

    • M.S. Smith
      September 11, 2010 at 12:14 am

      You're right in terms of performance. There isn't much difference in typical applications. But everything is moving to DDR3, so DDR2 will become obsolete regardless of the actual differences in performance.

    • MicroBuntu
      September 18, 2010 at 5:40 pm

      DDR2 isn't obsolete at all, there are still many capable systems out there running on DDR2 ram. Better yet, I'm currently breathing new life into my 2.9Ghz Celeron desktop with some new 1Gb DDR chips; thats right I said DDR, and a graphics card. I expect it'll have another 6 years of life before it becomes truly obsolete.