Bluescreens in Memtest and Prime 95

Hello together

A PC that I've built has bluescreens and crashes after some time of proper function. This Pc was NEVER overclocked.
The Pc also bluescreened when playing a very very old need for speed. These problems started a few weeks ago.

To make sure that it's no overheating/Gpu/Psu issue I took out the passive cooled Gpu which heated up the system and let the Pc run from the onboard Gpu. After that the PC didn't crash when playing the same old game but maybe I just didn't play long enough.

after an hour prime 95 small ffts testing the Pc crashed again (I don't know which kind of crash because I didn't watch it happen). This made me think that it has to be a Cpu/Ram/ or motherboard Problem.

As a next step I let prime 95 blend test run to see if it could be the ram... again crash. Then Memtest 86 crashed after 1hour.

Am I right in thinking that the ram is the problem? The CPU reached temps of 72C in prime (phenom II X4 955) could this also be the problem?

Specs: Cpu: Phenom II x4 955 CPU Cooler: Arctic Cooling Freezer 7 - Pro PWM Rev.2
Ram: Mushkin ddr3-1333
Psu: Xigmatec green 400-600 Watt (If you need to know it precisely I'll go to my friends place and check how many watts)
Mobo: Gigabyte GA-MA785GT-UD3H

the case has 1 front intake and one exhaust arctic cooling fan in the top back + the Psu exhausting heat from the top.

Thank you for your help

Kind regards Erdinger
5 answers Last reply
More about bluescreens memtest prime
  1. ok I let memtest run for many hours now without a crash so I guess it really is a cpu heat problem.

    I'll reapply the Cpu cooler with Arctic silver 5 and see if temps change.

    Do you think that the Arctic Cooling Freezer 7 - Pro PWM Rev.2 is adequate for cooling?
  2. Enough for not OCed untill slightly OCed.
  3. I do already have as5 and I make a dot on the middle of the Cpu and let it spread by applying pressure and slightly twisting.

    I think that I know how to apply thermal paste correctly since my Phenom II 720 with a Xigmatec hdts-1283 stays at 24C when idle and only reaches 53C in summer under prime when oced to 3.54 ghz...

    The Cpu cooler already had thermal greace applied so I don't think that it's possible that we falsly installed it, however I'll still try to reinstall it
  4. I went over to my friends house and installed the boxed cooler to make shure that the cooler wasn't causing all the problems. The CPU still reached 73C after a short time prime 95 although the fan was turning at 5600rpm (Loudly).

    I accidentally realised that the V core was 1.44 in CPU-Z which is much too high for a CPU at stock speed with bios defaults.

    I went into the bios and there was written that the setting was auto and 1.375 V again the real voltage measured by CPU-Z was 1.44 during prime 95 (V droop should decrease V)
    Then I decreased the V core by 0.025 V and after a reboot CPU-Z told me that the actual voltage was 1.33V. Thats a jump of 0.11 Volt although I only changed 0.025V in the bios.

    Then i decreased the Vcore by 0.050V (0.025 more) and it dropped to 1.30V.

    after running prime at these reduced voltages temps dropped by 15 degrees to a healthy 58C.

    My theory is that the CPU and PSU is fully functional and that the motherboard has a defect at bios defaults (and default voltages) and that the problem is solved now if the CPU is stable at the lower voltages.

    Do you agree with me?

    Thank you for your time
  5. The Cpu has different "load" states. as soon as it has some real work to do it powers up the highest "load" state with the highest frequency and the highest Voltage. (from app 20% load and higher)

    When you then increase the load even more up to 100% the power consumption increases and the Voltage drops because of a phenomenon called Vdroop.

    If I have understood my physics teacher then the Voltage drops because when the current (ampere) increases it uses up the voltage. although the Voltage is immediately raised again by the Psu or mobo it still reaches a lower value when under full load.

    Correct me if I'm wrong
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