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Dual Channel, DDR and Intel Processors

Discussion in 'PC Hardware' started by Christer, 2007/02/15.

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  1. 2007/02/18
    mattman

    mattman Inactive Alumni

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    I think you are getting to see what I mean. I can't argue against figures.

    From the way I see it (what I was trying to convey), you have an old stick of PC2100, how well could that be matched? You can't take it to a RAM manufacturer and ask them to match it (or you would be crazy if you tried :) ). Can you find the twin of that module? You can only buy them as a "twin pack ". Can you find the the same make and model? Maybe, but the synchronization may still be way out. Are you going to try another brand of module? The synchronization will probably be way out, but as Gary pointed out it may tell you that it is working as dual channel. You might then want to say, use Sandra to test the bandwidth (you might be happy, you might not).

    If trying to find a mate for the old stick to make matching pair may turn out to be a "prize draw" (we call it a Lucky Dip), I would go with an FSB that matched the system.

    Matt
     
    mattman,
    #21
  2. 2007/02/19
    Christer

    Christer Geek Member Staff Thread Starter

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    Chiles4,

    I guess that it is theoretically correct that you double the possible peak bandwidth but if you get it in real life is a different matter.

    In my friends case, going from 1 x PC2700 to 2 x PC2700 would mean a total bandwidth of 5400 GB/s but the processor is the limiting factor and the improvement would be 3200/2700=1.185 (~19%) and not 5400/2700=2 (100%).

    On a P4/800, going from 1 x PC3200 to 2 x PC3200 would give a 100% improvement, well, theoretically at least.

    Matt,
    I quote from the White Paper linked to in a previous post:

    I have come across P4/800 systems running "a matched pair" as well as "two of the same ". As Chiles4 pointed out, as long as it is indicated in BIOS that they run in dual channel mode, all should be well.

    Personally, I believe that the hype on "matched pairs" is only to be able to charge extra for the RAM. The key word is "believe" and yes ... :rolleyes: ... I am cynical but there was a hefty price premium in the beginning of the dual channel era!

    Christer
     
    Christer,
    #22


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  4. 2007/02/19
    Rockster2U

    Rockster2U Geek Member

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    Right Church, wrong Pew. (kinda) However, its time to change your beliefs. As stated earlier, I've been able to use two single Samsungs in dual channel and it has run quite nicely but I have not had the same experience with other manufacturers. Even had some very pricey Corsair XMS low latency that did not behave well with an exact duplicate. Most matched pairs are hand tested or so we are told. Regardless, I'm here to tell you there is a difference and there's more to it than a clever advertising campaign or some slick packaging.

    ;)
     
    Rockster2U,
    #23
  5. 2007/02/19
    Christer

    Christer Geek Member Staff Thread Starter

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    Rock,

    I threw in that hand grenade based on my experience with High Fidelity hardware in the nineteeneighties. They marketed matched pairs of loudspeakers. The only person who could detect the difference was the guy who matched them. It was an american who had his hearing insured for millions of dollars. It was also said the he could detect the difference between two pre-amplifiers built on the same specs components but from different manufacturers. Maybe all that was true in a controlled (laboratory) environment but in a home environment, I'm sure that the environment has a bigger impact.

    Back to RAM: I remember what you told about your experience with matched/unmatched pairs. I have personally not "seen it" but I don't build as many systems as you do so, I'll have to take your word as gospel ... :p ... !

    Christer
     
    Christer,
    #24
  6. 2007/02/19
    Rockster2U

    Rockster2U Geek Member

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    :D I'm humbled but that could get us both in trouble. :D

    Every manufacturer probably handles this differently. I discovered the Samsung compatability totally by coincidence - had run out of matched pairs OCZ and wanted to try firing up an ABIT NF7s - threw in two ordinary identical Samsung sticks and took a 2600+ Athlon Mobile (266MHz CPU) right up to 12x200 with no hiccups at stock voltages. (for reference, 3200+ stock is 11x200).

    ;)
     
    Rockster2U,
    #25
  7. 2007/02/19
    Christer

    Christer Geek Member Staff Thread Starter

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    Well, it was you who took us to the church ... ;) ... !

    You tweak the systems (overclocking) and I wonder if the same system that had troubles with mismatch, if it had been running on default settings would it be as sensitive to mismatch.

    Christer
     
    Christer,
    #26
  8. 2007/02/19
    Rockster2U

    Rockster2U Geek Member

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    No, its pretty black & white - either things run well or they don't. One can relax timings and get some forgiveness but the example I referenced is not an isolated situation. When it comes to dual channel boards, its best to buy matched pairs and eliminate the risk, but that's not enough - buy the good stuff - there is a much bigger difference in performance than in price.

    ;)
     
    Rockster2U,
    #27
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