EggXpert

Graphics Card Overclocking Guide

First step in overclocking a graphics card is to pick a fan speed that you are comfortable with the noise level. GPU stability is highly dependant on the maximum temperature that the card reaches while gaming so picking a fan speed other than auto really helps to keep the temperature stable.

If you were to graph the temperature and maximum stable clock speed it would look something like this as long as the voltage remained the same. Increased voltage will cause the maximum stable frequency line to move upwards on the temperature axis.

Now that the fan speed is set it is time to run the first stability test and find out the maximum temperature. I prefer rthdribl from http://www.mediafire.com/file/wdhjvrpuzellz59/Video%20Card%20Stability%20Test.zip for the stability test. It is more representative of a real game than something like Furmark but if you want absolutely perfect stability go with Furmark.

With my fan speed set to 100(I wear headphones so the noise doesn't bother me.) and clock frequencies at stock(675/1675/1100) my maximum temperature is 67C.

Core overclocking:

First clock I'll start working on is the core which is linked to the shader clock on nVidia cards.  On ATI cards there is not a shader clock. You will probably want to test in increments of about 25Mhz. I know my card quite well so I did rather large increments at first.

After moving core to 750Mhz my maximum temperature is 70C but the card remains stable so I'll continue to increase it.

Now it is set to 840Mhz and it reaches 69C before the drivers crash.

This leaves me with 3 options or a combo of them. A, decrease the temperature.(Not that easy since I'm on 100 percent fan.) B, Decrease the clock speed by a small increment until it becomes stable. C, Increase the voltage. I'll be using primarily option C with a little bit of A.

Now I've increased the voltage from 1.225 to 1.300. At 840Mhz it will reach 78C and still maintain stability.

At 860Mhz with the voltage increase it crashed at 73C. Time to add more cooling by taking the side panel off and a little more voltage.

With the side panel off and 1.332V it holds steady at 72C and no crashes.

880Mhz crashed at approximately 66C with the 1.332V. Time for more voltage.

At 1.408V and 880Mhz temperatures increase quickly to 78C causing it to crash.

Core overclocking conclusion:

Adding voltage will continue to put off the temperature limit but eventually the added heat from the higher voltage will cause it to reach the increased temperature limit.

With the side panel on and a minor voltage increase 840Mhz is the limit of my card. With the side panel removed 860Mhz is possible and 880Mhz is possible for short benchmarks.  Not bad for a card that starts out at 675Mhz.

Memory Overclocking:

Memory overclocking is mostly the same as core overclocking. Leave the core overclock at the highest stable setting and start increasing the memory slider and allowing the card to reach maximum temperature between memory frequency increases.

On an ATI 5K or 6K series card it is necessary to run a scored benchmark such as 3D Mark 11 between each memory speed increase as they use ECC to prevent crashes. Instead of crashing the performance will be degraded.

Test Setup:

http://s306.photobucket.com/albums/nn251/thebluemeanie1/?action=view&current=DSC_1321.jpg

http://s306.photobucket.com/albums/nn251/thebluemeanie1/?action=view&current=DSC_1322.jpg

Good job.

 

I have the Gigabyte 6850 and it runs COLD! its made to OC.

 

Its stock core is 820Mhz, I cant figure out how to change the Voltage, i went into the settings and i clicked the allow Voltage change but still wont let. Also what does Memory clock speed do if i increase it?

You probably need to change unofficaloverclocking = 0 to = 1 in the MSIAfterburner.cfg.  MSIAfterburner.cfg is in the MSI Afterburner install directory and can be opened and edited with notepad.

Memory clock speed increases the memory bandwidth which in turn improves the performance.

So you'll almost always need to set the fan speed to something other than auto? In essence then, it will not spin down to lower speeds in most cases?

You can use auto but some cards(like the GTX 480) will let reach a temperature like 96C before running the fan 100 percent to cool it down to 90C and then turn the fan back down to allow it to heat up again.

Using a set fan speed just makes it much easier to find the maximum stable temperature.

Oh okay I see.

I think if I were to overclock the GPU to that point in my system I'd adopt a water cooling solution.

In overclocking a video card, would the higher priority be on the Core and Shader clocks or the Memory clock? Will adjusting one be more noticeable in-game?

Right now on my 560 ti, I have the Core at 945mhz, Shader at 1890 and Memory at 2190.  I had to knock them down a bit because I was getting random crashes at 950/1900/2200.  I've seen people O/C some of these cards up to 1000mhz, so I was wondering if I should sacrifice some of my memory overclock to try and up the core or if that wouldn't make a noticeable enough improvement in gameplay.  My memory came at 2100 factory o/c'ed I believe.

n8great321:

In overclocking a video card, would the higher priority be on the Core and Shader clocks or the Memory clock? Will adjusting one be more noticeable in-game?

Right now on my 560 ti, I have the Core at 945mhz, Shader at 1890 and Memory at 2190.  I had to knock them down a bit because I was getting random crashes at 950/1900/2200.  I've seen people O/C some of these cards up to 1000mhz, so I was wondering if I should sacrifice some of my memory overclock to try and up the core or if that wouldn't make a noticeable enough improvement in gameplay.  My memory came at 2100 factory o/c'ed I believe.

Only way to tell is to run a benchmark like Unigine Heaven. Some cards are more limited by bandwidth than Core or Shader while others are the opposite. 

you have done an excellent job on this article.For us newbies,it's a big help understanding how all these new fangled gizmos operate as well.Of course, the last time I was "into" computers, they ran 3.3 d.o.s. and had green screens so...lol anyway should I use that msi program or sum'n else for my twin 6770,s? I had trouble getting them to x-fire or watever and don't want to disturb that. thanks,

snorris16:

you have done an excellent job on this article.For us newbies,it's a big help understanding how all these new fangled gizmos operate as well.Of course, the last time I was "into" computers, they ran 3.3 d.o.s. and had green screens so...lol anyway should I use that msi program or sum'n else for my twin 6770,s? I had trouble getting them to x-fire or watever and don't want to disturb that. thanks,

Thanks. 

MSI Afterburner is pretty much just a skinned version of Rivatuner which is the only other option I can think of.  They both work about the same since Afterburner is built off of Rivatuner.

I know this is an old post, but I'm new to these forums and been reading around...love it here! :) So thought I'd pipe in..

I like MSI Afterburner as well, though I'm currently using EVGA Precision. Don't know how long it's been around, but another option currently for OC software.

I don't know if every one knows, (or that it matters much) that the Shader Clock for Nvidia cards, is most likely double your Core Clock. The two clocks seem to stay linked in that way, although there's an option to unlink. As for an older card I had, a GeForce G100 (OEM Product) (don't laugh): the Shader was at 1400MHz and the Core at 567MHz and I was able to OC the Core all the way to 700MHz unlinked from the Shader. OCing a low end card only gave me a low end OC'd card...lol. But some limitation prevented me from going any further with it.

I've recently upgraded to a ASUS GT520-1GD3 for a temporary hold over til I get my parts for my new rig. I have been able to get the card up to 1010MHz Core /2020MHz Shader /640(x2?)MHz stable enough to watch HD Videos; but, a normal OC for gaming set to 988MHz/1977MHz/630MHz. Have a fan blowing right on the card from side panel to keep it under 78C max benchmark/60-65C normal gaming, etc...

As for the fan speeds, SpeedFan does have the option to control GPU fan speeds, right? Mine is passive so IDK. Or even the new ASUS software on their new boards, and others(?). But by now there is a way to control fan speeds for GPU?

But anyways, thought I would add to the bunch, and as I said, I love it here. Hope to see yous around!

Figured I'd add some clarification, 

EVGA Precision is simply MSI Afterburner with a different GUI (They both run on the same backend of RivaTuner) Any GTX 400 or above has what's called a Strapped Shader.. What this means is that the Core Clock and Shader are permanently linked to one another and are required to be linked to one another. For Fan Speeds, Both MSI Afterburner and EVGA Precision allow you to change a graphics cards fan speed.

 

As far as Speedfan goes, its c**p now in my honest opinion and doesn't work with really any modern hardware anymore.