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Cannot overclock my HD 7870 Sapphire OC edition?

Last response: in Graphics & Displays
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July 4, 2012 8:13:02 PM

Dear forum,

I was playing now around for 2 days to get my graphics card overclocked.
But everytime i overclock her, and start 3d mark 11, it just gives me some weird screen.
I read reviews froma anandtech, hardwareluxx and hardcop, and don´t know how they did that.
I did everything explained but no success.
Any suggestions?

I appreciate every help!
a b U Graphics card
a b K Overclocking
July 4, 2012 9:47:03 PM

You're going to need to be a bit more specific than "some weird screen."

Specifically, how much are you trying to overclock. Are you increasing voltage when you increase the clock speed. What tool are you using for overclocking. What guide were you following. What do you mean by "some weird screen." Does your screen go black? Does your computer bluescreen? Are you getting graphical artifacts?
July 5, 2012 5:29:27 AM

Hi, sorry for not being specific.
My screen has some weird artifacts when i start the test in 3d mark 11. Like black and some lines etc. I was using first triXX and followed the guide from hardcop.com they could overclock it to 1270mhz coreclock and 1560mhz memory clock with voltage ant 1.3v. With voltage at stock clock they could overclock to 1245mhz and 1560mhz. i tried both and both results gave me some artifacts. THen I tryed the settings from anandtech in catalyst with 1150mhz core clock and memory 1425mhz. Again artifact. So i don´t know what´s the problem? :/ 
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July 5, 2012 5:51:52 AM

At stock clock it start with no problem the 3d mark 11 test. But oced it starts and then the lines or something and then i have to restart. the core clock stays oced but the memory and voltage not. do i have to get better values and play around with mem clock and voltage ? i wonder just how they did it and i cannot.
a b U Graphics card
a b K Overclocking
July 5, 2012 2:16:52 PM

Every card is different. You can't just use somebody else's voltage and clocks, you have to find what your card can do.

Those artifacts are a result of your overclock being too high. You need to try lower values to find out what the maximum overclock your card can handle is.
July 5, 2012 2:52:20 PM

Oh i thought every card is the same. How should i test it than to set the highest? Should i do every mhz a new test and reboot of pc or is there any trick? :S
a b U Graphics card
a b K Overclocking
July 5, 2012 11:14:25 PM

You don't need to go in 1 MHz increments, but generally you want to start low and work you way up. A good trick to use is actually "binary search," a type of computer search algorithm.

The idea is you take your minimum (base clock rate) and maximum (the max overclock you've already tried) and split the difference. So if you tried 1000 and found it unstable, with 800 as your base, you'd try 900 next. You just keep repeating until you find the right number.

So, using the starting points of 800 and 1000 it would go like this.

800 minimum, 1000 maximum, try 900. If it works, 900 is your new minimum, otherwise it's the new maximum. For the example, we'll assume it works.

900 minimum, 1000 maximum. Try 950. Doesn't work.

900 minimum, 950 maximum. Try 925. Works.

925 minimum, 950 maximum. Try 937...

And so on and so forth until you're satisfied with the clock or your min and max are the same.

Also, I'd recommend reading some general guides on overclocking before you go any farther. Not reviews of your card where they overclocked it, actual overclocking guides. It's not a good idea to jump into overclocking without really knowing what you're doing. Pushing your chip too hard, or using too much voltage can literally kill it.
July 5, 2012 11:28:13 PM

oh thank you very much :)  I think the only problem is now the vOltage i don´t understand. is my 550w from corsair enough to handle that oc?
July 5, 2012 11:32:32 PM

and what program should i try each time when i oc ? 3d mark 11 and then reboot every time when artifact? :S
!