E8400 only one core fails Prime95

Hi All,

I've been running my E8400 @ 3.6Ghz sometime now for efficiency sake, but I went to bump up to 4.0Ghz. She wouldn't boot until until I hit 1.30v on the core, but in Prime95 core0 failed right off the bat and core1 ran for a couple hours. So I bumped to 1.32, 1.34, 1.36, and 1.38. Same problem, core0 fails and core1 keeps running. I noticed in CPU-z that my voltage is bouncing around with a Vdrop of 0.2 to 0.3 (which is a bit high?). I have stepping disabled and all the other CPU control bios, so I'm wondering why my voltage is bouncing around? Could I have a bad core?


EP35-DS3L (all the energy saver crap is off when OC)
2x2GB Patriot DDR2-6400 (when OC I leave at 5-5-5-15)


6 answers Last reply
More about e8400 core fails prime95
  1. You should not increase Vcore more than 10%.
    Lower your overclock or improve your cooling.
    It is normal to have some Vdroop.
  2. Does the core pass at 3.0GHz? and at 3.6GHz?
  3. In order to OC to 4Ghz, your ram is having to run at 888Mhz (assuming a 1:1 ratio).
    It may be that the ram cannot handle this speed.

    Try loosening the timings more and see if this helps.
  4. evongugg: the E8400 should handle up to 1.4v and stay within air cooling temps and I did go up in .02 voltage increments. I'm running a 120mm Zelman sink, @ 4.0Ghz it idles at 32c and 48c under load, so I don't think temp is a problem.

    drysocks: yes, the core passes at 3.0 and 3.6 with flying colors @ stock voltage.

    Jay_l_a: I have ram set to 5-5-5-15 right now (stock 4-4-4-12) and memory frequency was at 890Mhz (2x445)


  5. here is my bios specs, any thoughts?

    Robust Graphics Booster___________ [Auto]
    CPU Clock Ratio ____________ [9]
    CPU Host Clock Control_ [Enabled]
    CPU Host Frequency (MHz)__________ [445]
    PCI Express Frequency (Mhz)_______ [100]
    C.I.A. 2__________________________ [Disabled]
    System Memory Multiplier (SPD)____ [2.00 ]
    DRAM Timing Selectable__800__ SPD _890_ [Manual]

    Performance Enhance = [Standard]

    CAS Latency Time________________ 5
    Dram RAS# to CAS# Delay_________ 5
    Dram RAS# Precharge Delay_______5
    Precharge Delay (tRAS)__________ 15

    ACT to ACT Delay (tRRD)_________ auto
    Rank Write to READ Delay________ auto
    Write to Precharge Delay_________ auto
    Refresh to ACT Delay______________ auto
    Read to Precharge Delay__________auto
    Static tRead Value_______________ auto
    Static tRead Phase Adjust________ auto

    System Voltage Control____ [Manual]
    DDR2 OverVoltage Control__ [+0.4v to 2.2v]
    PCI-E OverVoltage Control_ [Normal]
    FSB OverVoltage Control___ [Normal]
    (G)MCH OverVoltage Control [Normal].
    CPU Voltage Control_______ [1.3675]

    Limit CPUID Max. to 3.....................: [Disabled]
    No-Execute Memory Protect............: <- Enabled
    CPU Enhanced Halt (C1E)................: [Disabled]
    C2/C2E State Support....................: [Disabled]
    x C4/C4E State Support..................: [Disabled]
    CPU Thermal Monitor 2(TM2) ...........: [Enabled]
    CPU EIST Function.........................: [Disabled]
    Virtualization Technology................: [Disabled]
  6. just brought the multiplier up to 2.4, Prime95 running stable for about 30mins, failed at test3 when the multiplier @ 2.0, if it runs like this I'm going to try dropping my timings down to 4-4-4-12
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