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Core2 Overclocking: Hints and Tips

Discussion in 'Hardware' started by Highland3r, 23 Nov 2006.

  1. Highland3r

    Highland3r Minimodder

    25 Jul 2003
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    This guide provides some tips and tweaks for getting the most out of your shiny new core2 system.

    Overclocking a Core2 is similar to clocking an A64, as the chips come with downward selectable multipliers. Overclocking basics can be found here

    There are specifics to both 965 and 975 boards which overclockers should be aware of. Both boards have their advantages and disadvantages, being aware of these could help improve your overclock.
    Users of NVIDIA boards would like your thoughts and feedback as much of what’s said below may not be applicable to you guys!

    So, let’s start off with the 965 chipset.
    - Due to the lack of "down clock" memory dividers, users only have options to run ram at a 1:1 ratio or higher. This isn't a huge issue; it just means if you're board runs out of FSB you can’t push your CPU any further.
    Unless you're running an E6300 this shouldn't be a problem for most users as CPU speed will be the limiting factor well before motherboards start to max.
    - Some users may experience an FSB wall at between 350 and 380 FSB. Try booting at 401 FSB or higher and see if that helps. It seems, at 400 FSB the 965 boards drop to a higher chipset strap which loosens the chipsets internal timings. You do however need to be aware that you'll need around 430-440 FSB with the same memory timings to compensate for the looser chipset timings. You may find its worth running close to the "changeover" point to achieve the best performance (390-399 FSB)

    975 boards -
    - These boards *tend* to max at around 450 FSB. vMods will probably be required to push higher. The vMCH option in bios should help you out here however, this is the chipset voltage. Wouldn't run above ~ 1.7 for long periods of time and make sure you add a fan over the chipset to keep things cool. (1.8v maybe suitable with upgraded cooling, however this isn’t recommended)
    - 975 chipset offers down clock dividers for the ram (i.e. ram can be run slower than FSB speed). This is useful if your ram runs out of headroom and there’s still scope to push the FSB further

    The below now appears not to be the case.

    Both 965 and 975 boards (Please note, this info is still under investigation by Tony and Freecableguy at The Tech Repository below info was taken from a thread there.)

    It has been found that the CPU multiplier comes into play when the Northbridge speed is calculated.
    So, for example stock E6600 has a multiplier of 9.
    The Northbridge clock = (stock multi/set multi) * FSB

    In the case of a stock E6600 running at 500FSB, the NB speed = 500 MHz (9/9)*500

    However, drop the mutli to 6 and we see a different story (9/6)*500 = 750 MHz.

    So, what does this mean for the overclocker? Well, it means you need to be careful when using non-default multipliers on your CPU. Dropping the multi may well drop your CPU speed but you need to be aware it will probably be increasing your Northbridge speed.
    Care especially needs to be taken when memory testing where often using a low CPU multiplier is used to find the maximum memory speed. In such situations, using up clock memory dividers offers a solution which alleviates this problem.

    However this feature also has its uses. It does allow you to fathom out the maximum FSB your motherboard should be capable off (assuming other components do not limit the FSB) Dropping the multi will allow you to test the limits of your motherboard.

    Nvidia Chipsets
    (Need to read up on 680i, should be similar theory to the 650 however. More tips to be added as they emerge)

    These boards DON'T suffer the same NBCC issue as the Intels do, so its possible to drop the CPU multiplier without pushing up the internal northbridge speed.

    If you get no boot's at certain FSB's, try setting either the memory or CPU (when running async/unlinked clocking) to an FSB ending in 2,4 or 8.

    As always any mistakes/comments/additions please post them.

    Last edited: 23 Feb 2007
  2. Highland3r

    Highland3r Minimodder

    25 Jul 2003
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  3. zahir

    zahir What's a Dremel?

    23 Feb 2007
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    Useful articles, just I got a lot knowledge from it....

    Last edited by a moderator: 20 Apr 2007

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