Overclock Your Videocard

Nathan Edwards

You’ve already pushed your CPU to the edge and taken your RAM to its outer limits.Now it’s time to put the screws to your videocard.

Every company that sells videocards based on an AMD or Nvidia GPU starts out on fairly equal footing: When building their products, all companies follow the same reference designs and clock-speed guidance that AMD and Nvidia provide.
One of the oldest and easiest ways for these vendors to differentiate their products from the competition is to drop a free game in the box. Another popular tactic is to offer a more generous (or more fault-tolerant) warranty. But the sexiest way to stand out from the crowd is to overclock the card’s GPU and memory. AMD and Nvidia both frequently sandbag their reference designs, leaving headroom for third-party manufacturers to goose the components’ clocks, which can easily wring more performance from a stock card.

Many board manufacturers offer the same GPU and memory configuration in more than one SKU, tacking a premium to the price tag of cards that feature higher clock speeds. But consumers can play the overclocking game, too—without having to pay a penny in premiums. We’ll show you how to use a free utility to easily squeeze more frames per second out of just about any videocard on the market.

But keep these facts in mind: Not every GPU is overclockable to the same degree. AMD and Nvidia intentionally segregate parts that exhibit a propensity for overclocking and then sell these for a higher price than less-pedigreed cards. As you push your GPU to the edge, variables ranging from the quality of your power supply to the build quality of your motherboard and the ambient temperature of your environment also come into play. Refer to the benchmark charts in this article to see how far we were able to push our cards but know that your mileage may vary.

Three Simple Steps to Goosing Your GPU

Using the free utility RivaTuner, you can push the speed of any AMD or Nvidia videocard that’s not currently running at its full potential

We chose RivaTuner over the overclocking utilities that AMD and Nvidia provide for one simple reason: This free third-party program offers far greater user control. The ability to permanently set a card’s fan speed, the flexibility to play with the GPU’s core clock (either separate from or in sync with its stream processors), and the capacity to create overclocking profiles for various computing scenarios are just a few of the ways RivaTuner stands out from other utilities.

To get started with your overclocking adventures, download RivaTuner (version 2.06) from www.guru3d.com . Click Yes to install available updates and accept the program’s configuration defaults. RivaTuner will create a registry database, which might take a few minutes. Read the excellent readme file while you wait, especially the FAQ.

Now you’re ready to begin. The steps for overclocking an AMD GPU are slightly different than they are for overdriving an Nvidia GPU, so proceed to the appropriate section for further instructions.

Overclocking an AMD Videocard

Overclocking an Nvidia Videocard

Overclocking an AMD Videocard

Step One: Set Fan Speed

In RivaTuner, click the Customize button in the Target Adapter box and then click the videocard icon to open a dialog box labeled “Low-level system tweaks.” Click the Fan tab and then place a check mark next to “Enable low-level fan control.” We want to see how far we can push the GPU, so we need to keep it as cool as possible. To do that, click Fixed. Now, push the slider all the way to the right (to 100 percent) and click Apply.

If the noise bothers you, set the fan speed to a lower value (but realize that you won’t be able to push your card as far when using a lower fan speed). If you can tolerate the fan at 100 percent, place a check mark next to the box labeled “Apply fan settings at Windows startup,” place a check mark next to the box labeled “Restore fan settings after suspended mode,” and click OK.

Step Two: Adjust Core Clock Speed

Again, click the Customize button in the Target Adapter box and then click the videocard icon. Click the Overclocking tab and then place a check mark in the box labeled “Enable low-level hardware overclocking.” Take the software’s advice and reboot so that it can detect the default memory and core clock speeds. Relaunch RivaTuner after the system restarts.

Click the Customize button again and then the videocard icon to open the “Low-level system tweaks” dialog box. Place a check mark in the box labeled “Enable low-level hardware overclocking.” Now, use the Core Clock slider to begin probing the limits of your GPU’s core. If the core is stock-clocked, start with gross adjustments—say, 25MHz at a time (note: The arrow keys enable more precision than the mouse).

Use a smaller increment if the card is already overclocked or if your system becomes unstable immediately. The idea is to find the system’s outer limit; once you’ve done that, back down in 5MHz increments until the system appears stable. Once you’ve achieved that, place a check mark in the box labeled “Apply overclocking at Windows startup,” click Save, and then click the OK button.

Before moving on to overclock the memory, stress-test the system with a benchmark that can run unattended for at least one hour. We use the two Shader Model 3.0 tests from Futuremark’s 3DMark06 test suite because they can be repeated up to 99 times. The free version of 3DMark06 doesn’t run these benchmarks, but two other widely used stress tests are available for free: Nvidia’s GeoForms and Masaki Kawase’s Rthdribl .

Step Three: Adjust Memory Clock Speed

This step is identical to Step 2, except you’ll now be adjusting the Memory Clock slider. You’ll also want to bump your clock in smaller increments this time—say, 5MHz to 10MHz at a time. A warning icon in the form of a yellow triangle with an exclamation point will appear if RivaTuner thinks you’re getting too aggressive, but this isn’t necessarily a sign that you’re going too far; you won’t know that until you stress-test the system.

If the system seems stable, place a check mark next to “Apply overclocking at Windows startup,” click Save, and then click OK. Repeat your stress test for at least one hour. If you run into stability problems after adjusting the core or memory clock speeds, reopen the System Tweaks dialog box, click the Overclocking tab, and click the Default button to reset the card to its original values.

Before and After: Radeon HD 3870
Stock 775MHz/1.125GHz
Overclocked 851MHz/1.143GHz
3DMark06 Game 1 (FPS) 23.2
24.4
3DMark06 Game 2 (FPS) 20.3
22.0
Quake 4 (FPS)
86.7
92.1
Supreme Commander (FPS)
30.0
30.4
FEAR (FPS) 57.0
59.0
Our test bed consisted of an Intel D975BX2 motherboard, an Intel 2.93GHz Core 2 Extreme X6800 CPU, and 2GB of Corsair DDR RAM.

Final Thoughts: Know your Videocard's Warranty

Overclocking an Nvidia Videocard

Step One: Set Fan Speed

In RivaTuner, click the Customize button in the Target Adapter box and then click the videocard icon to open a dialog box labeled “Low-level system tweaks.” Click the box labeled “Enable low-level fan control.” Take the software’s advice to reboot at this time, so it can detect the fan’s default state. Relaunch RivaTuner after the system restarts.

We want to see how far we can push the GPU, so we need to keep it as cool as possible. To do that, click Fixed. Now push the slider all the way to the right (to 100 percent) and click Apply. If the noise bothers you, set the fan speed to a lower value (but realize that you won’t be able to push your card as far when using a lower fan speed). If you can tolerate the fan at 100 percent, place a check mark next to the box labeled “Apply fan settings at Windows startup” and click Save. Place a check mark next to the box labeled “Restore fan settings after suspended mode” and click OK.

Step Two: Adjust Core Clock Speed

Now, click the Customize button in the Driver Settings box and then click the videocard icon. Click the box labeled “Enable driver-level hardware overclocking.” Here again, take the software’s advice and reboot so that it can detect the default memory and core clock speeds. Relaunch RivaTuner after the system restarts.

Return to the Driver Settings window in the main RivaTuner dialog box. Click the Customize button and then the videocard icon to open the System Tweaks dialog box. Place a check mark in the box labeled “Enable driver-level hardware overclocking” and select Performance 3D from the drop-down menu. Nvidia clocks its shader processors independently of the GPU’s core. RivaTuner defaults to linking the two components together, so increasing the speed of the core automatically and relatively overclocks the shader processors. We’ll leave them linked for this tutorial, but if you’re feeling saucy, experiment by unlinking the two by removing the check mark next to Link Clocks.

Now, use the Core Clock slider to begin probing the limits of your GPU’s core. If the core is stock-clocked, start with gross adjustments—say, 25MHz at a time (note: The arrow keys enable more precision than the mouse). Use a smaller increment if the card is already overclocked or if your system becomes unstable immediately. The idea is to find the system’s outer limit; once you’ve done that, back down in 5MHz increments until the system appears stable. Once you’ve achieved that, place a check mark in the box labeled “Apply overclocking at Windows startup,” and click the OK button

Before moving on to overclock the memory, stress-test the system with a benchmark that can run unattended for at least one hour. We use the two Shader Model 3.0 tests from Futuremark’s 3DMark06 because they can repeated up to 99 times.

The free version of 3DMark06 doesn’t run these benchmarks, but two other widely used stress tests are available for free: Nvidia’s GeoForms and Masaki Kawase’s Rthdribl .

Step Three: Adjust Memory Clock Speed

This step is identical to Step 2, except you’ll now be adjusting the Memory Clock slider. You’ll also want to bump your clock in smaller increments this time—say, 5MHz to 10MHz a whack. A warning icon in the form of a yellow triangle with an exclamation point will appear if RivaTuner thinks you’re getting too aggressive, but this isn’t necessarily a sign that you’re going too far; you won’t know that until you stress-test the system.

If the system seems stable, place a check mark next to “Apply overclocking at Windows startup,” click Save, and then click OK. Repeat your stress test for at least one hour. If you run into stability problems after adjusting the core, shader, or memory clock speeds, reopen the System Tweaks dialog box, click the Overclocking tab, and click the Default button to reset the card to its original values.

Before and After: GeForce 8800 GT
Stock 600MHz/900MHz
Overclocked 700MHz/1.025GHz
3DMark06 Game 1 (FPS) 26.4
30.5
3DMark06 Game 2 (FPS) 20.3
23.4
Quake 4 (FPS)
83.7
96.5
Supreme Commander (FPS)
29.1
31.3
FEAR (FPS) 71.0
81.0
Our test bed consisted of an Intel D975BX2 motherboard, an Intel 2.93GHz Core 2 Extreme X6800 CPU, and 2GB of Corsair DDR RAM.

Final Thoughts: Know your Videocard's Warranty

Know Your Videocard's Warranty

Familiarize yourself with your videocard’s warranty before overclocking it—some manufacturers are more tolerant of overclocking than others. Asus, for instance, will flatly refuse to honor a warranty on a videocard that’s been overclocked after leaving the factory. Diamond’s senior marketing manager, Lisa Legnante, told us, “Overclocking is not promoted or recommended; however, we know that it happens.”

EVGA and XFX, on the other hand, have a liberal attitude about the matter. “EVGA will warranty cards that a customer overclocks as long as there is no physical damage to the product,” said EVGA’s director of technical marketing, Joe Darwin. EVGA and XFX both allow you to change the card’s cooler, too—provided you don’t damage the card in the process and that you retain the original cooler in case you need to return it to the manufacturer.

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