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Thread: DDR3-2400MHz On AMD's A10 Kaveri With Kingston's HyperX Beast

  1. #21

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    Quote Originally Posted by narciso View Post
    I would like to see how much scaling memory speed translate to haswell performance. I have seen some tests here in phoronix but they only tested to 1600mhz, and it shows performance scaling.
    Regarding dual rate ram, most ram now are dual rated (double sided ram).
    Thats not what it means. The sticks themselves aren't dual channel, they are independent of that. the memory controller is what dictates how many memory channels are available. Most chipsets for the last decade have been dual channel, where if you have 2 sticks of ram with the same capacity, CAS and speed installed in the proper slots the controller will split up the data being split up and sent to the individual channels for increased bandwidth.

    It's the same thing you see with GPUs and their bit rate, the increased bitrates are more channels being added to the GPU's memory controller. On low end GPUs you'll see various memory setups on the same chip, these are because the manufacturers are allowed allot of leniency in what they use, most of them support 128-bit GDDR1-2-3-5 but can be found in a setup as low as 32 bit, which is caused by the manufacturer only installing higher capacity memory chips on one channel to cut costs.

    Now that said, AMD had previously stated that increasing the number of memory channels on a CPU only system results in increased latency and generally ends up as a wash performance wise. With a GPU in the mix I've got no idea if quad channel system ram would be of help for the APU as the increased bandwidth may help the GPU side but hurt the CPU side on latency.

  2. #22
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    Dual Rank (not Rate, typo in my original post) has nothing to do with Dual Channel.

    It's about the internal structure of each RAM module.

    And Double Sided doesn't necessarily mean Dual Rank, of my 3 module pairs (all double sided) only 1 is Dual Rank, the other 2 pairs are Single Rank.
    But for most RAM Modules it should be true, Double Sided=Dual Rank.
    Last edited by ObiWan; 01-24-2014 at 07:15 PM.

  3. #23
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    Default AMD Kaveri: dual ranked RAM provides significant performance gains


  4. #24
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    By the way, if you are using an APU, you will see better performance using 2400mhz DDR3 in single channel than 2133mhz DDR3 in dual channel.
    EDIT: I mean specifically in video games and such.
    Dunno why though.
    Last edited by profoundWHALE; 01-25-2014 at 12:50 AM.

  5. #25
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    Quote Originally Posted by profoundWHALE View Post
    By the way, if you are using an APU, you will see better performance using 2400mhz DDR3 in single channel than 2133mhz DDR3 in dual channel.
    EDIT: I mean specifically in video games and such.
    Dunno why though.
    -
    According to AMD Kaveri develops its full power only when each of the two memory channels of the APU two memory banks ("Rank") addresses or addresses.
    -
    http://translate.google.com/translat...er-speicher%2F

  6. #26
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    Quote Originally Posted by profoundWHALE View Post
    By the way, if you are using an APU, you will see better performance using 2400mhz DDR3 in single channel than 2133mhz DDR3 in dual channel.
    EDIT: I mean specifically in video games and such.
    Dunno why though.
    Huh... that's not what I would have expected -- is there a link or something I could look at ?

    Is there any chance the comparison was one stick of 2400 vs 2 sticks of 2133 with both connected to the same channel ?

  7. #27
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    Quote Originally Posted by bridgman View Post
    Huh... that's not what I would have expected -- is there a link or something I could look at ?

    Is there any chance the comparison was one stick of 2400 vs 2 sticks of 2133 with both connected to the same channel ?
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    due to the memory controller Kaveri APU ... the architecture of the memory modules (dual-rank vs single-rank) are essential for maximum performance.
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    "That the memory plays an important role in efficient APUs AMD generation "Trinity" has been known. With Kaveri, the problem will be further exacerbated because in addition to the play clock rates and the number of modules and their internal organization of a role. So lie between two single-rank modules DDR3-1866 and two dual-rank modules DDR-2400 quickly than twenty percent performance difference, in extreme cases, there are still significantly more." - http://www.computerbase.de/artikel/p...-mediaespresso

  8. #28
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    Nowhere in the computerbase article is single channel even mentioned, they tested Dual Channel Single Rank vs Dual Channel Dual Rank RAM.

    So instead of ~15% more performance between 1833 SR and 2400 SR, it was more than 20% to 2400 DR. (on the average 2400DR was 7% faster then 2400SR, both Dual Channel)

  9. #29
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    Quote Originally Posted by ObiWan View Post
    Nowhere in the computerbase article is single channel even mentioned, they tested Dual Channel Single Rank vs Dual Channel Dual Rank RAM.

    So instead of ~15% more performance between 1833 SR and 2400 SR, it was more than 20% to 2400 DR. (on the average 2400DR was 7% faster then 2400SR, both Dual Channel)
    Ahh, you think profoundWHALE was talking about single/dual rank rather than single/dual channel, ie saying that 2133 dual rank could outperform 2400 single rank with the same number of channels ? If so, that could make sense, at least on certain workloads -- seems that the Kaveri memory controller is able to interleave multiple memory banks on the same channel. AFAIK using 2 channels still makes the biggest difference though...

  10. #30
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    Well on some of the computerbase benchmarks Dual Rank was up to 30% faster than Single Rank, which could bring it close to Dual Channel benefits.
    (but only on that benchmarks)

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