i5 2500k overclock needs high voltages

Hi, I'm overclocking my cpu with stock cooler and Gigabyte z77-d3h motherboard and 2x4ghz 1600mhz ram.
People in this forum said they used their CPUs at 4.2ghz with stock voltages.
I tried to overclock mine to 4.2ghz but without LLC even at 1.28v, it gives BSOD. When I tried with LLC medium or high and 1.26v It runs well on daily use but cannot pass IntelBurn test and gives BSOD with prime95 blend test. Also when I use LLC, idle voltage seems so high at 1.26v.
Should I use LLC and what is the issue?
Reply to karacoglan
6 answers Last reply
More about 2500k overclock high voltages
  1. Well, for starters every chip is different and since it's a 6 year chip, it might not behave as it would when it was bought.

    Generaly, you should use LLC since it helps with vdroop during high loads.... High should be more than enough for 4.2Ghz.
    To make sure what LLC setting you need, you can run some quick stress tests and check how much your voltage drops under load... if it drops too much and BSOD's , you need to put it higher.

    Secondly, the fact that your idle voltage stays at 1.26 is because you probably haven't set an offset value in the bios, you have disabled power saving features (like c-states,speedstep or whatever gigabyte calls them) or have messed about with the power performance settings on windows. You should test without setting an offset value until you find your "right" voltage anyway.

    A BSOD in your tests isn't necessarily due to the CPU....it might be your RAM (you should always test with XMP off) or even your power supply/motherboard misbehaving.... what are your temperatures prior to crashing?

    Lastly, don't test with the new versions of prime95, but intelburntest and/or AIDA64.

    Best of luck!
    Reply to Maebius
  2. Thanks for the reply, now It can run at 4.2ghz 1.26v and high LLC. I disabled XMP and system bacame more stable.
    As for idle voltage it still remains at 1.26v. I enabled c3/c6 states and EIST. Clock ratio drops to x16 but voltage remains the same. I cannot set an offset voltage (dynamic vcore for gigabyte) because it is greyed
    Cpu temp rises to 85C at intel burn test, I know it is high, I will buy a better cooler.
    Reply to karacoglan
  3. I can't remember with gigabyte but I think you set the cpu voltage to normal and use a DVID (?) setting and then the voltage will also drop when idle.

    Once you get it stable, you can start manualy inputting your dram timings in the bios... with my 2500k, the auto settings through XMP only worked upto 4.5Ghz and from then on I had to set them manualy upto 4.8Ghz.

    85C in IBT isn't too bad... if in gaming your temps are around 60-65C you're just fine... although 1.26 for 4.2 can be considered mediocre (but not unexpected due to the age of the chip).
    Reply to Maebius
  4. karacoglan said:

    Hi, I'm overclocking my cpu with stock cooler


    Stop what you're doing, remove the overclock and buy an aftermarket CPU cooler.

    If you're setting a manual VCORE (which you should for overclocking) then disable any BIOS power-saving features that can dynamically adjust clock speed or voltage, such as C6 and EIST.

    The Prime95 Blend test doesn't push the CPU to 100% load; you need to run the Small FFTs test for that.

    LLC is mostly relevant if you want to run an overclock 24 hours a day.
    Reply to bicycle_repair_man
  5. I am just testing limits of my CPU before buying a cooler. I am planning to upgrade HD7850 to rx 580 or GTX 1060 so I want to unsure my cpu is sufficent for such graphics cards. I am using power saving features to lower idle voltage and power consumption. If you say this is unnecessary, I could disable.
    Reply to karacoglan
  6. Testing the limits with the stock cooler is pointless as the limit will change the moment you install an aftermarket cooler.

    You'll be absolutely fine with an RX 580 or GTX 1060. It's only when you step-up to a GTX 1070 that an overclocked 2500K would start to make a difference.
    Reply to bicycle_repair_man
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