MaximumPC 2008 03

40 MAXIMUMPC | MAR 08 | http://www.maximumpc.com

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.

STEP 3

STEP 1

OVERCLOCK

YOUR VIDEOCARD

OVERCLOCKING AN NVIDIA VIDEOCARD

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

STOCK OVERCLOCKED

775MHz/1.125GHz 851MHz/1.143GHz

Our test bed consisted of an Intel D975BX2 motherboard, an Intel 2.93GHz Core 2 Extreme X6800 CPU,

and 2GB of Corsair DDR RAM.

BENCHMARKS BEFORE AND AFTER: RADEON HD 3870

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 soft-

ware’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 2 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 video-

card 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 compo-

nents together, so increasing the speed of the core automati-

cally 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 lim-

its 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

OVERCLOCKING AN NVIDIA VIDEOCARD