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overclocking incompatibility with PCI-E 2.0

Discussion in 'Overclocking & Cooling' started by modder, Oct 7, 2008.

  1. modder New Member

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    hello,
    i have a big problem,I changed my old 8800 gts graphics card (PCIE_16 rev1.0) by a new HD4870 (PCIE_16 rev2.0)
    and now i can't overclock my cpu Q9450 :cry:.
    result blank screen with one short bip post code or bios checksum error .:banghead:
    my System Specs:
    gigabyte P35-DS4 rev 2.1
    2 x PCI Express x16 slots (The PCIE_16_1 slot supports x16; the PCIE_16_2 supports x4.)
    GC powercolor HD4870 512 PCS+

    vga bandwidth limit ? any idea ?

    nb:isn't my first oc ,but this time i'm out
  2. TRIPTEX_CAN

    TRIPTEX_CAN

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    So the system run perfect with the CPU at stock speeds?

    If so.. does it post even with a 5Mhz increase on the FSB?
    modder says thanks.
  3. modder New Member

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    So the system run perfect with the CPU at stock speeds? yes
    If so.. does it post even with a 5Mhz increase on the FSB? no

    Hard drive LED blinking like boot load ok, but not display anything!always bios checksum error and dual bios load default bios F9.i tried all bios release (f9,f10,f12,f13,f14a)
    nothing has changed .
  4. Sasqui

    Sasqui

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    Can you lock your PCIE bus to 100 or lower?

    Past experiences I've seen PCI clocks not at what the BIOS says, but close - based on some strap/multiplier. If you underclock the PCIE bus, you may find it works.

    Some graphics cards are much more forgiving than others with an overclocked bus.
    modder says thanks.
  5. modder New Member

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    i tried 95,97,98,99,100,101,103 mhz PCI clocks and not work.i think ,the bios isn't optimized for overclocking cpu with HD4870 graphic card.
    i have two problems
    1 -bios checksum error.i could be solve it with bios modded ( default CPU FSB set to 333 mhz instead 100 mhz original bios).because after all error my Q9450 run with 100 mhz cpu fsb (100mhz*8=800mhz q9450 couldn't run at this speed)and generate an error =bios checksum error
    2-no display after cpu overclocking.?????? no idea

    Possible my PSU (750 W) does not provide enough juice? http://www.thermaltakeusa.com/Product.aspx?C=1264&ID=1502#Tab1
  6. BarbaricSoul

    BarbaricSoul

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    your PSU shouldnt have a problem running your system.

    1st thing I would try is resetting your bios. Pull the battery out of the motherboard for a few minutes, then re-seat the battery and see if that helps.
    modder says thanks.
    Crunching for Team TPU
  7. modder New Member

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    I trying tomorrow your tip (Pull the battery out of the motherboard)
    I can also overclock slightly (2.66 ghz to 2.8 ghz)when I set northbrige voltage to auto.
  8. Sasqui

    Sasqui

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    If you are seeing a 100 Mhz FSB, something is wrong... I think a BIOS reset is a good idea. Also the NB V change giving you *some* ability to overclock sounds like a voltage issue.

    Do you have the card powered by two 6-pin PCIE connectors on different cables?
  9. erocker

    erocker Super Moderator Staff Member

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    I think you are having driver issues. Are you sure everything dealing with your old 8800 have been removed. Drivers, registry entries etc..?
    modder says thanks.
  10. Sasqui

    Sasqui

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    Doesn't sound like it as he can't even post with 5Mhz OC.
    modder says thanks.
  11. modder New Member

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    it works :) Q9450@3.6 Ghz
    I removed the battery -- results: bios checksum error fixed (the date and time have changed ,with a clear cmos (basic method with jumper) time and date doesn't change)
    PCIE bus to 101
    NB set to +0.175 V <---- the culprit

    before (with 8800gts),NB set to 0.25V max for more stability
    now (with HD4870),NB set to 0.175V max ,if i set NB more than 0.175V ,my display not work.STRANGE ?
    it seems that the OC settings are completely differents with a new vga.I was accustomed to the old parameters.

    thank you all for your help :) Now I can have fun
  12. BarbaricSoul

    BarbaricSoul

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    yeah :toast::D
    Crunching for Team TPU
  13. OnBoard

    OnBoard New Member

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    That's about the weirdest thing I've heard in months :) Good that it works now.
  14. Sasqui

    Sasqui

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    Ditto - hooray, problem nailed! :toast:

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