E6400 hitting a wall at 2.66Ghz?

I also posted this in the motherboard section, but it seems this section gets a little more traffic and my question is relevent to both.

Hello, I've been having some strange overclock hold backs, and other forums have failed. I think the TG forums will be a little more helpful :D; any advice is appreciated. My system is as follows:

MSI P965 Platinum mobo

Core 2 Duo E6400

1Gb (2x512Mb) Crucial Ballistix DDR2-800 4-4-4-12

Antec 500W Smartpower


Zalman CNPS9500

Here's my problem:

My old Asus P5ND2-SLI with an nForce4 chipset was horribly unstable and finnicky with hardware changes, and finally totally conked out. But while it was working, it would overclock my old Pentium D 805 to 3.8 reasonably stablely but with heat issues, and rock solid to 3.6. After it died, I prepared for Core 2 by purchasing the MSI P965 Platinum. However, it wouldn't even post the PD805 at 3.8, it was unstable at 3.6, and was only solid at 3.4. This was with the exact same cooling and voltage settings, and keep in mind 3.4 is only a 170Mhz FSB, far below its maximum.

For Christmas, I got my E6400, and was excited to pop it in. 2.4 rolled around easily with no voltage bump, 2.66 perfect, but then, with 2.7 and beyond, Prime fails immediately regardless of voltage and the system will lock up. Temps are ideal, 27C idle and barely breaching 44C load, I set my RAM severely underspec to rule that out, 5-5-5-18 at DDR2-667, updated the BIOS, turned off most available BIOS options, bumped north bridge voltage, etc. etc., I just can't figure it out. The current FSB is only 333Mhz, which is commonly and easily exceeded with my setup. I would just say I got unlucky, but the fact that 333Mhz FSB for an e6400 is so uncommonly low and the motherboard has proven it underclocks sub-par with the PD805, I think there's something I'm overlooking. It also seems that adjusting the voltage in the bios is very unresponsive to stability, most of the time only making it worse. Is it possible the VRM is just defective?

My other current prime suspect is a BIOS option I'm unaware of, or perhaps just some other general aspect I missed out on. I have fairly good overclocking experience and have read extensively into the subject, but this anamoly has me stump. Please share if you have experience with this mobo or this type of overclocking wall before I buy a new Gigabyte DS3.

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More about e6400 hitting wall 66ghz
  1. Your Asus board probably had a better VRM so it could clock high with 805D. 805D is a power beast.

    But regardless of the VRM I think you just could have hit the FSB wall on the MSI board. I have read some old reviews and the MSI boards didnt look good on ocing with high FSB. This could have changed significantly with newer bioses.

    I say why bother so much. Buy what other ppl buy. If they say DS3 can hit 500FSB than you will probably have about the same success. I think the S3 is just as good from what I have read, it's a lot cheaper, doesnt have all solid caps but the important ones (VRM) are solid.

    Take a look on this link http://www.anandtech.com/mb/showdoc.aspx?i=2882&p=4
  2. Hi JuiceJones,
    Now right away I am thinking your memory is going way past 667MHz.
    You must set the memory to 533MHz! When set at this speed, it is synchronous with your 266 FSB coreclock.
    Then when you increase FSB to 300 and 333 etc, the RAM also goes faster to match.
    Using CPU-Z, at 333FSB you should get 667DDR memory.
    I set my RAM severely underspec to rule that out, 5-5-5-18 at DDR2-667

    But if you select DDR2-667 in BIOS, that will not be what you get at 333FSB - you get will ~833DDR using other than 1:1 synchronous ratio.
    To get 333MHz memory (667DDR) with the default 266 coreclock, that is a 4:5 ratio.
    To get DDR800 memory with the 266 coreclock, that is a 2:3 ratio.
    Different mobos have different setup terminology (confusing).
    Gigabyte describes the synchronous 1:1 condition as "x2" multiplier, ie. with 400FSB you will get 800MHz memory...
    ABit uses FSB:memory ratio.
    Anyway, try that (and confirm with CPU-Z that you have it synchronous).
    In theory you should get 3.2GHz from 400FSB x 8, with 800DDR memory speed.
    Or you could quit at 333FSB! 2.66GHz is very fast Core2 CPU - you will like it.
    In that scenario, your memory will be 667MHz and you could get nice tight 3,4,4,10 timings at the less-than-rated memory speed (like I do).
    Let us know if this helps,
  3. Wow, the CPU thread was immediately much more responsive, heh.

    Thank you for your input OGS, but I am aware of the RAM ratios and the like, and when I said I was running it at 667, I ment I selected the 533 option in the BIOS for a 1:1 ratio.

    And NaDa, thank you as well, despite the fact 333Mhz seems abnormally low, even for the MSI, it's a possibilty I've considered. True, 2.66 is plenty fast for what I do, but as an entusiast it's a little dissapointing.

    I still have that PD805 sitting around, so I guess I'll just save up my cash, get a new board and let my mom get the room heater :P.
  4. Not to hijack this thread but ... :)

    I just bought a 680i mobo and am planning to get an E6600. I am planning to get DDR2 1066 (PC2 8500) memory. This would give me a 1:1 ratio between memory and fsb? This would be the optimal memory speed choice? Meaning I wont have to fuss with timings to get a 1:1 ratio... should match up right out of the box?

    Thanks in advance for any feedback.

  5. No, all current Core 2s have a 266 (1066 quad pumped) FSB.

    A 1:1 ratio without overclocking is DDR2 533, since DDR doubles the FSB. You would need a unheard of 533 FSB to run DDR2 1066 in a 1:1 ratio.

    If you don't plan to overclock, save some money on that RAM.
  6. Yes - exactly.
    Hey Jones, are you running your RAM @ at least 2.0V?
    Many just don't work at (default) 1.8V.
    Some work, but not too well... which sounds like yours.
    Goose that RAM - loose timings and healthy voltage. :D
    You should get a nice steady 333FSB (even with the MSI, it should be okay IF it allows RAM voltage adjustment).
    @ Preecher
    Core2 can save you a bit on memory, compared to AMD AM2...
    DDR2-533 is just fine! whereas DDR2-800 would be recommended for AM2.
    DDR2-667 will allow you a good Core2 OC.
    The DDR2-800 will allow you a real stout Core2 OC (from 266 to 400 FSB coreclock).
    Like JuiceJones said, DDR2-1066 would actually be 1:2 ratio (which apparently the latest nVidia 680 mobos will do).
    The trick is: you gotta leave your FSB on stock 266MHz! If you want any OC at all, stick to 1:1 (and save your money).
    Again - over-rated memory is good, to a point, because it will offer very tight timings at a slower (synchronous) speed. But that primo PC2-8500 stuff is just robbing your vidcard budget, y'know?
  7. Heh, they're running at 2.2V, but still any of your ideas are appreciated, since 333 as a limit is dissapointing.
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