What is DDR3?

To provide compatibility and interchangeability for computer memory, the structure and form factor are controlled by a standards organization known as JEDEC. JEDEC specifies voltages, speeds, timings, communication protocols, bank addressing, and many other factors in the design and development of memory DIMMs. Taking a closer look at publications at www.jedec.org can provide insight into what DDR3 brings to the market and where it might go. Comparing DDR2 and DDR3 several interesting points stand out.

Official JEDEC Specifications
  DDR2 DDR3
Rated Speed 400-800 Mbps 800-1600 Mbps
Vdd/Vddq 1.8V +/- 0.1V 1.5V +/- 0.075V
Internal Banks 4 8
Termination Limited All DQ signals
Topology Conventional T Fly-by
Driver Control OCD Calibration Self Calibration with ZQ
Thermal Sensor No Yes (Optional)

Please keep in mind that JEDEC specs are official. They are a starting point for enthusiast memory companies. However, since there was never a JEDEC standard for memory faster than DDR-400 then DDR memory running at faster speeds is really overclocked DDR-400. Similarly DDR2 memory faster than DDR2-800 is actually overclocked DDR2-800 since there is currently no official JEDEC spec for DDR2-1066.

DDR speeds ran to DDR-400, DDR2 has official specs from 400 to 800, and DDR3 will extend this from 800 to 1600 based on the current JEDEC specification. Initial DDR3 offerings will be 1066 and 1333 will quickly follow. The 1333 speed is important because it matches the 1333 bus speed of the new Intel processors. The 1333 processors can run any speed of DDR3 or DDR2 memory, but 800 and 1067 will be overlap speeds with DDR2. 1333 will be the first DDR3 speed to offer enhanced memory speeds to current and future processors.

Since DDR3 is designed to run at higher memory speeds the signal integrity of the memory module is now more important. DDR3 uses something called "fly-by" technology instead of the "T branches" seen on DDR2 modules. This means the address and control lines are a single path chaining from one DRAM to another, where DDR2 uses a T topology that branches on DDR2 modules. "Fly-by" takes away the mechanical line balancing and uses automatic signal time delay generated by the controller fixed at the memory system training. Each DDR3 DRAM chip has an automatic leveling circuit for calibration and to memorize the calibration data.

DDR3 also uses more internal banks - 8 instead of the 4 used by DDR2 - to further speed up the system. More internal banks allow advance prefetch to reduce access latency. This should become more apparent as the size of the DRAM increases in the future.

DDR3 further reduces the memory voltage. In the past few years we have moved from 2.5V with DDR to 1.8V with DDR2. DDR3 drops memory voltage to 1.5V, which is a 16% reduction from DDR2. There are also additional built-in power conservation features with DDR3 like partial refresh. This could be particularly important in mobile applications where battery power will no longer be needed just to refresh a portion of the DRAM not in active use. There is also a specification for an optional thermal sensor that could allow mobile engineers to save further power by providing minimum refresh cycles when the system is not in high performance mode.

There is even more to DDR3, but for most enthusiasts looking at a new desktop system DDR3 can provide higher official speeds, up to 1600MHz. The higher speeds are available at lower voltage, with 1.5V as the official specification. There are many features that will not make much difference in DDR3 performance until we begin to see even faster and higher capacity memory. The question, then, is whether DDR3 memory provides better performance for the computer enthusiast than current DDR2?

Index DDR3 Memory and P35 motherboards
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  • RichyDitch - Tuesday, February 17, 2009 - link

    Hey there, I'm still not sure what would be better. I have an AsRock P35 motherboard, and am totally confused as to what would be better when it comes to DDR2 or DDR3.

    The motherboard it's self can hold up to 8gb of PC2 8500 1066mhz duel channel DDR2 memory, and up to 4gb of PC3 10600 1333mhz duel channel DDR3 memory.

    What would end up being better, if I get the max amount of memory for the motherboard. The DRR2 specifications I mentioned or the DDR3 specifications mentioned?
    Reply
  • mikegonzalezrubio - Saturday, January 24, 2009 - link

    I WANNA BUY A NEW LAPTOP BUT I DONT KNOW WHAT IS THE BEST CHOISE IS BUY A DDR2 LAPTOP OR DDR3 LAPTOP MY OPTIONS ARE:

    HP - Pavilion Laptop with Intel® Centrino® 2 Processor Technology - Bronze/Chrome
    Model: dv7-1285dx
    WITH
    Intel® Centrino® 2 processor technology with interrelated Intel® Core™2 Duo processor P8600
    Intel® Wi-Fi Link 5100AGN (802.11a/b/g/n) network connection and extended battery life capability.
    6GB DDR2 memory
    For multitasking power, expandable to 8GB. 1066MHz frontside bus, 3MB L2 cache and 2.4GHz processor speed.
    Multiformat DVD±RW/CD-RW drive with double-layer support
    Records up to 8.5GB 17" WXGA high-definition widescreen display
    With BrightView technology and 1440 x 900 resolution
    500GB Serial ATA hard drive (5400 rpm)
    NVIDIA GeForce 9600M GT graphics

    *LINK OF THE PRODUCT http://www.bestbuy.com/site/olspage.jsp?skuId=9166...">http://www.bestbuy.com/site/olspage.jsp...&typ...


    OR TO BUY A DELL Studio XPS 16
    WITH
    Intel® Core™ 2 Duo P8400 (3MB cache/2.26GHz/1066Mhz FSB)
    LCD PanelEdge-to-Edge HD Widescreen 16.0 inch WLED LCD (1366x768) W/2.0 MP
    8X DVD+/- RW(DVD/CD read/write) Slot Load Drive
    Specifications - DVD+/-RW or Bluray Drive
    4GB2 Dual Channel DDR3 SDRAM at 1067MHz (2 Dimms)
    320GB3 7200 RPM SATA Hard Drive
    ATI Mobility RADEON® HD 3670 - 512MB4
    Intel® 5100 WLAN Wireless-N (1x2) Half Mini Card
    LINK OF THE PRODUCT IS http://configure.us.dell.com/dellstore/config.aspx...">http://configure.us.dell.com/dellstore/...kc=produ...
    WHO CAN TELL ME WHAT IS THE BEST CHOICE HERE BETWEEN THOSE LAPTOP...?
    thanks for your help i wait an aswer
    sincerely
    MIGUEL ANGEL
    Reply
  • Shadowmaster625 - Thursday, May 17, 2007 - link

    quote:

    Two conditions would shift the recommendation to DDR3 instead. When DDR3 prices come close to DDR2 then buy DDR3 instead. More significantly, when DDR3 becomes available at higher speeds and/or faster timings then definitely choose DDR3 if you are looking for performance - even if the price is higher.


    No there are not just two conditions. There is a third condition that I wish you'd start considering: How it screws over everyone who wants to upgrade. This article has proven that Intel can squeeze more performance out of their memory controller. What this ultimately shows is that improvements in memory controller design actually outweigh the change to a new memory standard! Is DDR2 18% faster than DDR? (Maybe now, just barely. After 3 years!) Yet intel just pulls a new memory controller out of their wazoo that does 18% better? I smell a big rat and anadtech aint talking about it.
    Reply
  • TA152H - Thursday, May 17, 2007 - link

    You're not the first person to be frustrated by how poorly memory speed increases, but there are a few things to consider.

    For one, the new controller is NOT 18% faster than the old, that is only in bandwidth, not latency. Latency is VERY important, and discounting is a huge fallacy. And yes, bandwidth has increased a lot more than 18% from DDR.

    Secondly, this isn't by any means the end of DDR2, it's a forward looking move that paves the way for DDR3. DDR2 will continue to dominate the market, and by the time it's obsolete you'll have DDR3 ready. What would happen if Intel waited for DDR2 to already be obsolete before they introduced DDR3? You'd have that long wait while memory companies worked on the new technology, and prices were very high and performance wasn't what it should be. After a couple of years, DDR3 would finally be mature in performance and cost, but nearly obsolesence itself. So, Intel is just getting things started so when DDR3 does become necessary, it is ready. It's like a pipelined processor, Intel is starting DDR3 in stage one while DDR2 is in stage 2.

    Also, keep in mind that DDR2 is not made to go much faster than it is, and will run into a wall. That's where DDR3 comes in. Again, it's forward looking by Intel. DDR2 can still increase a bit, but by the time it runs into a wall, DDR3 will be right there to go to higher speeds.

    Also keep in mind the number of people that upgrade is very, very small. It's not their intention to screw people over, but it's something they are willing to do because of the importance of evolving technology, and the miniscule percentage of people that upgrade processors without motherboards. It's a necessary evil.
    Reply
  • sprockkets - Wednesday, May 16, 2007 - link

    quote:

    We can tell you that Intel does not really have an NDA, but they have been very aggressive in holding first tier manufacturers to a May 21st performance embargo and retail distribution on June 4th


    Funny how we can let you benchmark hardware not coming out till this Autumn but we can't let out any info or benchmarks on a new chipset coming out in 5 days.
    Reply
  • cornfedone - Wednesday, May 16, 2007 - link

    Anyone who thinks 2-5% increase in system performance is a big deal needs to get their head examined as it don't mean nothing real world. Most people couldn't even see a 2-5% system performance increase on their best day. Bearlake is more hype with no tangible performance increase. Reply
  • TA152H - Wednesday, May 16, 2007 - link

    Wow, that's a really uninformed remark.

    You might not notice X-Rays, but they can kill you. So don't talk about this babble with tangible (it's a poor choice of words, since it literally means "touchable" and it's bad enough Anand overuses it) and what's noticeable. You're getting an amazing increase from a chipset, and this is the mainstream chipset. On top of that, it supports DDR2 and DDR3 so it pushes the technology envelope forward. Getting any increases in memory performance is simply amazing at this point, since chipsets are so mature it's not like there is a low hanging fruit, and Intel processors have such a large cache it makes memory performance less important than would otherwise be. It's a fantastic chipset, arguably the next 440BX. I knew it was good, but even I'm shocked at just how good it is. Kind of kills the argument for the on-die memory controller, which I never was completely sold on. It's scary though, it makes you wonder just how well Intel will do with that if they can get this type of performance with the memory controller on the chipset.

    It's an amazing chipset, it is shocking in terms of performance, so much so I doubt anyone thought it was possible. Give them their kudos when they deserve it, because they do with this bad boy. I wish I knew how they did it, but my guess is by finally moving their chipsets to modern lithography, they were able to include a lot more buffers and run it faster without using too much power. I am really clueless though, that's pure speculation. I don't know how they made this so much better than everything else. It's shocking.
    Reply
  • bldckstark - Wednesday, May 16, 2007 - link

    Shockingly enough, 2% is within the error of the tests performed, and therefore is not, statistically speaking, significant. Not only that, but the cost of progress is passed on to the consumer, who usually rates the speed of their computer based upon how fast their favorite website loads, not on how fast it performs computations. Shocking, I would say. Reply
  • TA152H - Wednesday, May 16, 2007 - link

    So, you're saying that on every single test by weird coincidence, the Bearlake is higher just be statistical scatter? You're saying the huge increase in bandwidth is somehow also weird coincidence?

    How do you know what the margin of error is anyway? When you get repeatable results where one is always higher, you can conclude pretty easily that they are real and not statistical scatter.

    And you know the cost of Bearlake how? You are sure it's more expensive? It probably uses less power, since it's made on finer lithography. So, you're talking about something you probably don't know anything about. I do agree that most people don't need the latest and greatest, so I fundamentally agree with that part, but who is going to make them buy this chipset? If they want cheap, they can still buy something cheap, if this isn't, which I don't know. But, some people need performance, and this is a great item for that, and it's a real accomplishment from Intel.

    By your perverse logic, all improvements that don't increase web speed are immaterial. That's clearly wrong. That only applies to some people.

    You're completely illogical.
    Reply
  • OrSin - Wednesday, May 16, 2007 - link

    Thats total system performance, from 1 part. Memory performance is 16% and that huge from a low cost part. Unless your adding a $400 video card over $200 card you will not notice the diffenecen either. One part theats 15% more in price then a similar part will rarely give you 5% improvement.

    Remember this is a systems and it mean each part gives some improvement to make a better system.

    Yeah you will not notice 5%. Bet then why get a part that works 5% slower when the cost is similar. Some people are never happy.
    Reply

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