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i7 860 / GA-P55-USB3 / F3-16000CL9D-4GBTD

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  • i7 860 / GA-P55-USB3 / F3-16000CL9D-4GBTD

    I'm preparing to build 2 new machines with the components listed in the subject line. I don't intend to overclock the CPU or memory, but I do want to adjust BIOS settings so the memory is running at it's max speced speed of 2000MHz.

    I have a couple of preliminary questions, if I may. I have found two threads here that may contain relevant information - and

    The first of these contains what it says is a complete set of settings for the correct memory on a Gigabyte P55 based MB, very similar to mine. The second mentions what it says is a setting missing from the first set.


    1) Why do some of the voltages listed in the 'complete' set for the i7-860 contain three values? (For instance, 'QPI/VTT Voltage 1.150v ............ 1.100V [1.190V]'). What is the significance of these 3 values? Which one am I supposed to use?

    2) Message 5 in the second thread I've linked to says that the 'complete' settings list is missing a value for QPI/VTT, and says a correct value is 1.4V. Is this correct?

    3) Finally, is XMP a total failure, then? Both the motherboard and RAM are supposed to support it. Shouldn't I be able to simply enable XMP and let the system automatically make the necessary BIOS modifications?

    Thanks for your time.

  • #2
    1) Sorry, what that is is default, what's it's operating at, and what to set it at. That should be how it shows up in BIOS, which is what I was trying to replicate or display. So what you should use is the value in brackets, but, technically you will want to find the lowest stable value for your specific system as it differs from CPU to CPU.

    2) The QPI/VTT Voltage varies from CPU to CPU, so the values we suggest are guesstimates or base points based on our own testing of the CPUs we have. As stated, you want to find the lowest stable voltage for each memory frequency. As memory frequency goes up, this value will need more.

    3) No, it does set the frequency, timings, and voltage of the memory. It will also adjust CPU frequencies and such if necessary, but the one thing is can not adjust is the QPI/VTT Voltage. It is not the "XMPs" fault. Although they can actually set this, as ASUS does on some motherboards, it is still a guesstimate and may not always work. Essentially it is hit or miss, or a lucky guess. You still need to test and find the lowest stable voltage for your specific CPU.

    With DDR3-1600, the motherboard can automatically overvolt the QPI/VTT Voltage and supply enough to operate. But with DDR3-2000+, just like any overclocking, manual settings will always be needed. This is why Intel only recommends DDR3-1333, as anything above that is considered overclocking and will need "tweaking" to stabilize.

    Thank you


    • #3
      Thanks very much for the quick response!

      1) Very good - I understand.

      2) Again, very good.

      3) So a reasonable approach would be to enable XMP, then manually adjust the QPI/VTT voltage to a known good (hopefully) value at the high end of it's range, and then, over time, experiment with lowering it to find a stable minimum. Correct?

      So, if I were to do this, I take it that 1.4 is a reasonable 'known good' value, high enough that it should be stable, correct?

      What would be the downside of simply leaving the VTT at 1.4V? Does it reduce the device lifetime? Consume more power, run hotter? What is the trade-off I'm trying to balance?

      And thanks again for the info, and your time.


      • #4
        3) Yes, you can simply run stress tests to see if the system is stable under load. These programs place your system under essentially 100% load, so if anything is unstable, it'll error quickly.

        QPI/VTT Voltage 1.40V should be sufficient for DDR3-2000, simply lower to 1.35V and retest for stability, and so on. It does not need to be completely spot on, but within .01-.04V range would be good enough. Slightly too much or too less, it can be unstable. The only time it will reduce lifespan is if you attempt completely off settings and your motherboard allows it. What you are trying to do is supply just the right amount of memory controller voltage to support the voltage and amount of memory modules you have. The motherboard can tolerate slightly more or less voltage, but precision is always the key to a stable, long-lasting system. Many people wonder why their hardware goes bad over time, but many times it is because they use "AUTO" values so the motherboard can set it to whatever it wants, whenever it wants to. Consequently, when voltages become too high on one end, it can damage the hardware and eventually cause it to become defective. Luckily we have lifetime warranty to save you from that.

        Thank you