Prime95 Fail - Recomendations

I'm new to this, but I have read as much as I can here at on a few other sites. I'm relaying my information/setup/situation for recomendations. I really am more interested in some experience rather than a ridiculous fast machine.


Intel Core2Quad Q6600 Kentsfield (G0)
Gigabyte EP45-UD3P (F8 BIOS)
G.Skill DDR2 400 (4 x 8Gb) [5-5-5-14]
Sapphire Radeon 4850 (512Mb)
*Note: according to CPUZ*
Antec 650w PSU
Antec 300 Case
CoolMaster HyperZ 600R CPU Cooler

Vista 64 - Business
CPU-Z (1.50)
Core Temp (0.99.4)
HWMonitor (1.13.0)
Prime95 (25.8.4)


378 x 9 = 3.40GHz
VCORE: 1.36v(HWM) 1.3125v(Core Temp)
DDR: 1.89v(HWM)

All Voltages are set to AUTO
Al Timings are set to AUTO
All Other settings are STANDARD/DEFAULT


Prime95 - Blend
FAIL on Core #3 @ 3min [Test 2 - FFT 1024k - 52C]
FAIL on Core #2 @ 20min [Test 4 - FFT 8K - 54C]

STOPPED @ 48min
CORE #0 [MAX 58C]
CORE #1 [MAX 58C]

I have a decent understanding of OC theory (ie. knowledge w/o experience). I would like to get stable @ 3.4GHz. I would like to attempt 3.5 & 3.6 (for kicks). I do not understand RAM timings.


Up VCORE until I get stable/overheat (bad).
Adjust timings (?!?)

Rescale to 425 x 8

Thank you in advance. If you need more information, please let me know.

7 answers Last reply
More about prime95 fail recomendations
  1. Try to up the vcore a bit, and that should fix the Prime95 errors.
  2. Just a side thought.

    When I start to adjust my voltage should I take everything off AUTO and just set it to whatever AUTO was displaying.... or should I only adjust VCore from AUTO??
  3. "G.Skill DDR2 400 (4 x 8Gb) [5-5-5-14] "
    I am guessing that that is a typo.

    Leave the memory timings alone. They are slow enough that they shouldn't limit the OC.

    I take all my settings off "AUTO". You simply do not have any idea what the BIOS is doing or how it decided to do it.

    Gigabyte lets you save and restore BIOS setups from the [F11] and [F12] keys. Very handy and saves a lot of time.

    3.4 GHz. is up where chip variations start to come into play. I was able to reach 3.0 GHz. with my Q6600 without a vcore increase and 3.3 GHz. with a small increase. 3.6 GHz. took some tinkering.

    Here's what I would do (actually what I did) GA-EP35-DS3P:
    Take all the AUTO settings and change them to manual or Normal except PCI Express Freq, DRAM Timing (optimize this last), and Loadline Calibration.

    As you work your way up from stock freqs, you will reach a point where you will need increase vcore a little each FSB increase. Eventually (around 3.4 or 3.5 GHz) you will need a relatively large vcore increase to maintain stability. That's a very good place to stop.

    You may need to increase DRAM voltage to match factory specs. Normal is 1.8 volts. At around 3.4 or 3.5 GHz, you may need to start increasing the FSB and MCH voltage. I upgraded to a Q9550 so I don't remember what I had these set to.

    CoreTemp will tell you what your VID is. That's a really good place to start with the CPU voltage. My Q6600 (VID 1.2625 volts) settings:

    2.4 GHz. - 1.225 volts (yes, it was undervolted at stock)
    3.0 GHz. - 1.2625 volts
    3.3 GHz. - 1.325 volts
    3.6 GHz. - 1.45 volts drooping to 1.425 volts. Prime95 stable 72 hours. Core temps 61 - 65 C
    3.7 GHz - 1.52 volts drooping to 1.500 volts. Boots but unstable. P95 crashes within 5 minutes.
  4. An application that's made overclocking much easier for me is OCCT. It is a stress test and monitoring utility that can be used to test the CPU, RAM, video card, and power supply separately. If set to run with small data sets, it will test your CPU only. Large data sets will test your CPU, RAM, and motherboard. It has separate tests for the GPU and video memory. It will also monitor temperatures and voltages. OCCT usually reveals instabilities much faster than Prime. Feel free to use it to find out what aspect of your overclock(s) is unstable.

    With my Q6600 G0, I was able to get it stable at 3.2GHz with 1.4v. I probably could have pushed it further, but the room I have my computer in doesn't have great ventilation and at full load the CPU reaches 65 degrees Celsius internal temperature. It's not a good idea to exceed 65 degrees for long term use. Not all Q6600s are created equal so yours may overclock better (much better in some cases) or it may need more voltage to reach that speed.

    1.35v for a Q6600 is the upper end of the default voltage range, so it's safe to set it that high. You can then increase the speed in increments and test for stability each time (about 1 hour with OCCT will tell if your stable or close to it). It's also a good idea to disable extra CPU functions such as Speedstep as this can dynamically alter your voltages and multiplier, causing your system to become unstable.

    Usually a setting of 2.1v is optimal for most DDR2 800 memory sets. I don't recommend overclocking your RAM and CPU at the same time. As you increase your FSB to overclock your CPU, keep your ram at normal speed. This can usually be accomplished through the CPU/RAM ratio setting. Once you have your CPU stable, you can start increasing the RAM's speed.
  5. Yeah, don't trust the gigabyte board with it's auto settings since with auto it assumes you're not overclocking with the FSB. Read the overclocking sticky, and if you don't understand something Google it. Anyway you need a higher vcore, and probably a better CPU cooler.
  6. Thanks everyone for confirming my suspicion. I'll start by following some standard voltages and timings that I've been finding.

    Side question: I read the stickies regarding RAM and timings and my general understanding is that OCing RAM isn't really nessicary or productive. Is OCing RAM considered a bit overkill??

    I'll post my results when I'm stable
  7. Faster RAM does yeild faster results. For now though you should set your FSB:RAM ratio at 1:1 and loosen the timings as much as possible (the highest CAS ratings and so on). This is to ensure that you aren't limited by your RAM when overclocking. Once you've hit your overclocking limit, then you can try to set higher RAM speeds and tighten the RAM timings. Of course, not all RAM is created equal and you can burn it out by using too high a voltage, and in a few cases to fast a setting (heat damage mostly).
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