Why did new video card destabilise overclock?

had my i7 960 running at 4.2Ghz when i had my nvidia GTX 260 installed.

got my ati 6950 back from repairs, install it along with a clean reinstall of windows 7 and all of a sudden im getting horizontal lines scattered across the screen.

Why is it doing this?

The only voltages I changed for the overclock is vcore and qpi/vtt.

Is my qpi/vtt of 1.515v the problem?

It needs to be that high to keep my 24gb of ram stable.
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More about video card destabilise overclock
  1. Try the monitor on a different computer and/or try a different monitor on your computer.
  2. its not the monitor, cable or the pci-e slot, Ive checked all three.

    If I set the cpu back to stock speed there arent any issues.
  3. Do you have a specific need for 24GB of RAM?

    I ask because RAM performance actually drops as you add more RAM and you can't utilize more than 6GB except in rare cases. 24GB is only needed for people who are doing a specific type of video editing and need to have the video they're working on buffered in the RAM for easy access.

    Gamers require no more than 4GB or up to 6GB if they heavily multi-task while gaming.

    Video card:
    Your video card voltages have nothing to do with your RAM. You should not be overclocking your video card if that is what's corrupting it.

    All that RAM might be taxing your Power Supply, or causing voltage instabilities on your motherboard. I recommend trying this to see what happens:

    1) Drop to either 6GB or 12GB of RAM and use default settings
    2) Do NOT overclock the video card
    3) Do NOT overclock the CPU
    4) make sure BIOS is up to date

    Once things are stable you can try overclocking or adding more RAM one thing at a time.

    FYI, for video games your system is limited by the graphics card. Overclocking it provides little benefit but easily leads to instabilities. Overclocking your CPU has no effect. More than 6GB has no effect.
  4. Please given us the full specs of your rig, mobo, RAM (specs) and PSU.
  5. motherboard is gigabyte G1.sniper with f3a bios

    Ram is two 12gb (3x4) corsair dominator 1600mhz cl9 1.65v kits CMP12GX3M3A1600C9

    psu is corsair AX850

    I have using 24gb of ram because although the computer is a gaming and general use computer I run two minecraft servers in the background.

    I never said that i had overclocked my video card, I never do because I feel it just causes problems

    I was simply asking about the qpi/vtt because I assumed thats how the video card, ram and cpu communicated with each other

    I said that if I dropped back to stock setting for cpu and voltages that it works perfectly without any problems

    I just noticed a second newer beta bios (4b) and will try that.

    I really dont think that my psu would be having trouble.

    Im not going to drop the cpu overclock as I barely even play games anymore. the overclock helps startup times by quite a bit and generally just speeds up the computer a bit.

    I just find it strange that swapping the video card out would cause such problems. Its not like i went from a 8 year old card to a new one. I know the 6950 needs more watts but my 850w psu should have heaps of headroom. I bought the 850 so I could get a second 6950 later. I hope I shouldnt have bought the 1200 instead.
  6. Can you test the GPU in another rig and test your rig with another GPU? The GTX 260 work fine with the rig?
  7. I just took a screenshot with "print screen" and when I look at it the lines arent there.

    I know the cables and screens are fine so does this mean signal interference?

    I do have a power pack with about 8 things plugged in right behind the case, is this the problem?

    I have also noticed the wifi on my iphone has started dropping out which has never happened in 6 months of using it.

    Is this an indication of too much electronics or power in the room?
  8. through trial and error I can now say that i have no clue what is causing the problem.

    I have checked monitors, cables, drivers, windows 7 and now lowering the overclock isnt helping either.

    the video card is speeding up then slowing its fan 3 times over about 10 seconds before the computer starts to post, is this significant?

    I'm about to check the card in another rig so ill report back if that helps or not.
  9. Well I tried the video card in another computer and the same problem occurs.

    The weird horizontal lines are appearing and the computer often crashes when more than 1 monitor is plugged in.

    So to re-iterate the ati 6950 has the same problem in both rigs and both rigs work perfectly with the GTX 260.

    Time to get a replacement card perhaps?
  10. Quote:
    got my ati 6950 back from repairs, install it along with a clean reinstall of windows 7 and all of a sudden im getting horizontal lines scattered across the screen.

    Sounds like the card wasn't repaired after all.

    Could just be a lemon, fix one problem and another arises, like dominoes, one after another.
  11. ^Agree on that, not always a repaired GPU works.

    Regarding the "print screen", can you try with another monitor? even a LCD TV can works for check the problem. I'd think that the GPU is the problem, more when the fan doesn't start at the same time than the system start.
  12. Botched repair job...they should have just replaced it with a new one for you....now the shipping fees should start to get stupid....I bet they charged you to ship them their own bad product back to them just so they could turn around put it back in the box and ship it right back to you...They may have cleaned it up for you....Asus does this all the time you get a bad MOBO they frickin charge you to ship their bunk product back to them and never really fix anything except the shipping companies pockets
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