CAUTION: Overclocking can damage your graphics card (not covered by your warranty) so use the information of this post at your own risk.
Today, a small hardware tutorial: how to overclock a GeForce GTS 250 (1Gb GDDR3).
Why I need to overclock my graphics card? Overclocking your graphics card will allow you to get the most out of your card for free! You can expect a gain up to 10%!
This GeForce, from Twintech, was equiped with a really noisy cooler (and not efficient):
So first thing I did was to replace this cooler with a better one: the Scythe’s Musashi:
This cooler is really efficient and is very quiet!
Okay, now that the hardware side is in place, let’s see the software one. Basically, overclocking a graphics card is an easy operation: find the max graphics card’s clocks that keep the video card stable. By stable I mean no freeze nor artefacts. To find these max clocks, you need two utilities:
- RivaTuner: RivaTuner will allow you to changes graphics card clocks.
- FurMark: will allow you to burn the graphics card to check stability.
A GeForce has three different clocks we’re going to change: GPU clock, Shader clock and Memory clock. Before starting the overclocking, we have to know the graphics card default clocks. You can use RivaTuner for that, but GPU-Z gives you these values faster:
Twintech GeForce GTS 250 default clocks:
– GPU: 738MHz
– Shader: 1845MHz
– Memory: 1000MHz
And before starting the overclocking, let’s have a look at the FurMark’s score (1280×1024, fullscreen, no AA, 60 sec):
Now we can begin the graphics card overclocking. Here are the steps:
- 1/ launch FurMark
- 2/ launch RivaTuner
- 3/ do overclocking: increase one clock (GPU, shader or memory) by 5 or 10MHz while keeping the two others to their default values. Repeat this step until you see artifacts or notice a FurMark freeze. At this moment drop speed by 5MHz until you don’t see artifacts anymore.
- 4/ Once you have found the max clocks, set them all to their max values. I bet you will see artifacts on FurMark because all values to the max will produce more heat. At this point, drop the clocks until you don’t see artifacts anymore.
Let’s see each step in detail.
Start FurMark in stability test mode, in a 512×512 window with no AA, and check Xtreme Burning Mode:
Press I key to hide text on the 3D window (that will speed up a tad the rendering).
Start RivaTuner and display frequencies and temperature monitoring:
Now display low level settings:
RivaTuner will ask you to reboot in order to detect the graphics card clocks. But if your card is not overclocked, just click on Detect now:
Now RivaTuner shows you the default clocks:
Uncheck the Link clocks checkbox.
Now, we’re ready to find each max clock. Increase GPU clock until you see something strange (artifacts or freeze). In case of artifacts, drop the clock by 5Mhz until they disappear. After each increase, wait a little bit (30sec) before increasing the clock again.
With this GeForce GTS 250, exceeding max GPU clock causes a FurMark freeze (but on other cards, too high GPU clock may cause small dots). In this situation, the only solution is to click on Default button to restore default clocks. If you can’t do this, reboot your PC.
The max stable GPU clock I found is: 837MHz. About 100MHz in more!
Click on Default button to restore default clocks. Now increase Shader clocks until you see artifacts. With this GeForce GTS 250, exceeding max shader clock causes large artifacts on FurMark. Here is the video that shows artifacts due to a too high shader clock:
The max stable Shader clock I found is: 2074MHz. About 230MHz in more…
Click on Default button to restore default clocks. Now increase Memory clocks until you see artifacts. With this GeForce GTS 250, exceeding max memory clock causes small rectangular artifacts on FurMark. Here is the video that shows artifacts due to a too high memory clock:
The max stable Memory clock I found is: 1083MHz.
4/ Final Clocks
Now the final tuning. Set all clocks to their max stable values. You will certainly see artifacts with these settings because set all clocks to the max will produce more heat. But now, depending on the artifacts you see, you can drop the right clock. After each modification, wait at least for two or three minutes to be sure your graphics card is stable.
Here are the final clocks I found:
– GPU: 808MHz
– Shader: 2017MHz
– Memory: 1044MHz
As you can see, final clocks are different from previous max clocks found separately.
Now, let’s see the gain of this overclocking:
The gain of this overclocking is around 7.5%.
You can also run other benchmarks like 3DMark or your favorite video game to see overclocking gain or just to be sure that these new clocks are OK.
As you can see in this screenshot, the GPU temperature didn’t exceed 75°C with overclocked clocks. We can thank the Musashi VGA cooler that was able to keep GPU temperature relatively low.