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FSB voltage... what does it do?

Discussion in 'Motherboards & Memory' started by hat, Dec 8, 2010.

  1. hat

    hat Maximum Overclocker

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    Many of you may know I've been trying to overclock my E2140 on a 750i board recently. A big player in stability has been FSB voltage. I've never messed with a setting like this before. Really all I've ever bothered with is vcore and memory voltage, as I've always had CPUs with high multis that really didn't push the FSB that much (mostly AMDs, AM2 onward). My E2140 has an 8x multiplier, so it's taking a high FSB clock to really get it going.

    Question is: What exactly is FSB voltage? Which components are affected by it? How high is too high?
    Crunching for Team TPU
  2. newtekie1

    newtekie1 Semi-Retired Folder

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    I'm not to sure what FSB Voltage does, but I know with my Celeron E3200 on my 780i I have to up it to lessen the huge FSB holes the Celeron has.

    I think I have it set to 1.4v, and it definitely helps with stability.
    hat says thanks.
    Crunching for Team TPU More than 25k PPD
  3. mlee49

    mlee49

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    I thought it effected the North Bridge the most.
    hat says thanks.
  4. hat

    hat Maximum Overclocker

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    At 1.5v I get no dice with my E2140 at 333FSB... a frequency that should work at stock voltage, both for the FSB and the CPU.

    I thought that's what the north bridge voltage did... unless the north bridge is split up into parts with independently controlled voltages... like one being for the memory controller and the other for everything else the north bridge does?
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  5. mastrdrver

    mastrdrver

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    Does the board have GTL control?

    FSB voltage is kind of a drive voltage. As the FSB goes higher, the higher it must go (generally). It also is a high low voltage that is used to push data around the system on the 775 platform. This is where having GTL control is helpful since it declares a high/low voltage signal. If you don't get it right then the system will not know if the voltage signal is high or low and will crash.

    When FSB voltage goes up so will cpu and nb voltage. It's a kind of delicate 3-way dance with those voltages when pushing the FSB. Going wrong with any one of them will crash the dance. Usually fsb voltage > cpu voltage.

    There is a sticky on the XS Intel section of the forum about GTL voltage that covers it all. FSB voltage is not just a guess and go because you will more then likely miss and cause problems.

    Use LinX or IBT and watch your GFlops. The closer you get your GTLs to their target the closer the GFlop numbers will get. If you don't have GTL control then still use those two programs to do the same thing. You'll only have FSB voltage to adjust the results and you may have to skip some sections of the FSB to get to the next part that allows your GTLs to be correct.
  6. hat

    hat Maximum Overclocker

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    My board has GTLVREF, lanes 0-3. I can control each of them individually, in incriments of .05mv. What should I do with them? I tried setting them all to +70mv and leaving FSB voltage at default (1.20v) and booting at 1600FSB but it was a no-go.
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  7. hat

    hat Maximum Overclocker

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    I completely hauled off and set the GTLVREF to max on lanes 0 and 1 (figured I didn't need it for 2 and 3 because I only have a dual core, not a quad), FSB voltage to max, and NB voltage to max. Still didn't boot at 1600, then I tried 1550 and that didn't work either.
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  8. newtekie1

    newtekie1 Semi-Retired Folder

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    Judging by how the Celeron E3200 that I have is just a die shrink of the E2140 you have, I'm not surprised you are having problems.

    The FSB holes on these processor are gigantic, especially above 300FSB. My E3200 will not boot at 333FSB or 400FSB, even if I lower the multiplier to run it at a clock speed I know is stable.

    I think part of the reason these chips were binned so low is because of the low FSB wall they have.
    Crunching for Team TPU More than 25k PPD
  9. hat

    hat Maximum Overclocker

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    But other people were doing it on stock voltage with seemingly no problems at all, that's what gets me about it...
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  10. mastrdrver

    mastrdrver

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    Do you also have a NB GTLVREF?

    Read and understand

    All the GTL voltage reference is doing is saying either yes (high voltage signal) or no (no voltage signal or ground) when the voltage crosses the GTL voltage. As you push your FSB higher you have to increase voltage. No problem except more voltage creates a bigger "bounce" of the signal when it goes high or low. The real problem is mostly when it goes low as the "bounce" is bigger. In either case if the signal bounce crosses the GTL voltage again then the system will become confused and either bsod or similar (no post).

    If you can figure out that the GTL settings are doing (like adding the set mv to the default vGTL) then I can help you more. Also make sure you read the link and have some kind of grasp of what is going on. You don't need to fully understand it but you do need to understand what he is talking about and what you're trying to achieve.

    Stop doing this. More harm can come out of this then good.

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