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667 or 800MHz mobo, both running at 800MHz

Discussion in 'Overclocking & Cooling' started by Rob!, Oct 22, 2007.

  1. Rob!

    Rob! New Member

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    Hello all. I've been browsing for a while, did some searching, and I couldn't really find an answer to this question. I would also like to mention that I've been away from the PC world for a while (I crossed over to Mac :p), and I haven't messed with any components since my last PC (s754 Athlon with DDR400) quite some time ago.

    For example, say I have a 2GHz Athlon X2, running on either a 667MHz memory standard motherboard or an 800MHz. It'll run at 2GHz on either one, correct?

    Now say I up the FSB by OC'ing on the 667MHz mobo to 800MHz. Does the CPU get overclocked along with it to over 2GHz, or does it stay the same? Assume I'm using 800MHz RAM so that it can handle the overclock.

    And finally, which would yield better results: 667MHz mobo upped to 800MHz OC with 800MHz RAM, or an 800MHz mobo in which I dropped the mulitplier to make the RAM 667, and then upped it back to 800MHz again?


    I hope my questions are clear enough. And thanks!
     
  2. sneekypeet

    sneekypeet Unpaid Babysitter Staff Member

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    #1 yes
    #2 only if your mobo has the option to only clock the ram (if you specified which mobo , would help)
    #3 the first instance I belive would show better performance as you would take a loss running a divider in the first place!
     
  3. Rob!

    Rob! New Member

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    I'm planning well in advance on building a budget gaming computer before Christmas, so I haven't chosen parts yet. I probably wont spend more than $50 or so on a motherboard since my overall budget will be about $300.

    I already have a 2600XT that I put in my brother's PC, but I'll be taking it out and throwing it in mine if and when I build it, so I'm mostly concerned about CPU/RAM/mobo combos and what I can get cheap with still good performance.
     
  4. Darknova

    Darknova

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    Buy a board capable of DDR2 800Mhz, then if need be buy 667Mhz RAM, so that in the future you can buy some DDR2 800Mhz RAM and overclock even more.

    And yes, if you have the settings set up right you can keep the CPU at the same speed while increasing the RAM speed. :)
     
  5. largon New Member

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    Yup. But first you need to realize that memory frequency on A64 depends on CPU speed, and, naturally the divider.

    DDR2-667 would be like this:
    2000MHz / 6 = 333MHz (DDR2-667)

    AND

    DDR2-800 like this:
    2000MHz / 5 = 400MHz (DDR2-800)
    Yup. If you bump the "HTT", (no FSB on A64) you'd need atleast 240MHz to run 2400MHz on the CPU to get DDR2-800.

    BUT!

    You can also OC the memory alone (from DDR2-667 to DDR2-800) simply by setting a lower divider. As seen earlier a 2000MHz A64 generates DDR2-667 by dividing the CPU freq by 6 (2000MHz/6=333MHz -> DDR2-667), setting the divider higher (to 5) would make it DDR2-800.
    There's 2 ways (and 2 ways only) to OC to DDR2-800 from DDR2-667 starting with a 2000MHz CPU (multiplier: x10):
    #1:
    Forcing a higher upward divider (from 6 to 5) -> 2000MHz / 5 = 400MHz (DDR2-800)

    OR

    #2:
    Bump the HTT from HTT200 to HTT240 thus OC'ing you CPU -> 2400MHz / 6 = 400MHz (DDR2-800)

    Which way do you mean? But I reckon above example is enough of an answer for your question...
    You can't really do this. Once you lower the multiplier, RAM divider will follow AND RAM freq will actually rise because dividers on A64 are actually integer values either added (=downward dividers) or substracted (=upward divider) to the CPU multiplier.

    RAM freq wouldn't drop to DDR2-667 unless you set another divider OR LOWERED the HTT:
    Starting point is as follows ->
    10*HTT200 / 5 = 2000MHz / 5 = 400MHz (DDR2-800)
    Then drop the multi to 9 and bump the HTT ->
    9*HTT240 / 4 = 2160MHz / 4 = 540MHz (DDR2-1080)
     
    Rob! says thanks.
  6. Rob!

    Rob! New Member

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    EDIT: A lot got posted while I typed, nevermind.

    EDIT2: So from what I understand from the last post, the divider and mutliplier are different numbers. How come the HTT (or what I've been calling FSB) is 200MHz, and the RAM runs at 400MHz (800/2)?

    From what I remember from trying to overclock my last rig about two years ago, the bus speed (using the term loosely, I guess it's the HTT?) was 200MHz, and the mutli was 11. So 200x11=2.2GHz. The RAM speed was also 200MHz (DDR400). I'm used to them being the same value so I think that's throwing me off.
     
    Last edited: Oct 22, 2007
  7. largon New Member

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    The paragraph after the third quote in my previous post answers that... ;)
     
  8. Rob!

    Rob! New Member

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    I'm re-reading again and again, it's slowly sinking in :p

    So the HTT is what you adjust to overclock, which in effect makes the RAM speed a function of the CPU speed; I always thought of it the other way around.

    Man, I should start looking at those overclocking guides again.

    Thanks for all your help and for being understanding :D
     

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