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7900 GTX: How to get the best overclocks?

post #1 of 5
Thread Starter 
Ok i recently bought a BFG OC 7900GTX. As soon as I got it I installed a Zalman VF900 on it. It idles at around 34'c

The default clocks are:
Core: 670Mhz
Mem: 1.64Ghz

Now I could tell you all the ins and out of overclocking any CPU or RAM from the BIOS, but with GPUs i'm in the dark.

What I usually do is install the coolbits reg file, run "detect optimal frequencies" in the classic nVidia control panel. Then set my clocks to whatever it detects.

Is there a better way to overclock the GPU? preferably an automated overclocker which will run until it detects artifacts or overheating. Also is there any BIOS updates or tweaks I should know about, maybe to increase voltages?

Again, the more help, the more reppage
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post #2 of 5
Go download ATI Tool and run the "Max mem & MAx Core" tests.

That should do you fine.
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post #3 of 5
Don't use automation for overclocking if you want the best performance. Would you use automated overclocking tools on your CPU and memory? (I hope NOT!) Getting the best settings takes time. Here's my guide:

Overclocking Tools
There are two common overclocking tools, nTune/nVTweak and RivaTuner. They both are fine applications for overclocking so the choice is more of a personal preference. Do not bother using their auto detect method for overclocking. Manual overclocking provides better results. They and other applications later mentioned can be found on the list at: http://www.evga.com/community/messag...TOPIC_ID=17285

How to OverclockGo the respective application’s overclocking area and select manual overclocking. You will see two values, one is for the GPU while the other is memory. Unlike CPU and system memory, these two values can be overclocked separately so there is no need to worry about dividers. Leave the 2D speeds at stock, you do not need to overclock 2D speeds since they do not require much to process. However, do select the 3D speeds and these currently should match the 2D speeds. You will be overclocking only 3D speeds.

To find your maximum memory speed:
1) Leave the GPU core speed at stock.
2) Increase the memory clock speed by 5Mhz
3) Select the “Test” option
4a) If you pass, repeat step 2
4b) If you fail, back down the memory clock speed by 5Mhz
5) Increase the memory clock speed by 1Mhz
6) Select “Test” option again
7a) If you pass, repeat step 5
7b) If you fail, note the last passing speed.

Then to find your maximum core speed:
1) Reset the memory speed back to stock.
2) Increase the core clock speed by 5Mhz
3) Select the “Test” option
4a) If you pass, repeat step 2
4b) If you fail, back down the core clock speed by 5Mhz
5) Increase the core clock speed by 1Mhz
6) Select “Test” option again
7a) If you pass, repeat step 5
7b) If you fail, note the last passing speed.

You should now have your maximum core and memory clock speeds. Now, subtract 5-20Mhz from these two values as a safety margin and you now have your theoretical safe overclock speed. Set the core and memory clocks to these values and test. You should be able to pass the test now with both overclocked. Click to apply these 3D overclock speeds. One common issue is that users notice that their card’s memory speed is half the speed that is advertise on the packaging. This is because newer graphics cards use Double Data Rate (DDR) memory. They perform two operations per clock so their effective clock is twice of what is displayed. Also, there is a bug with ATITool that displays memory clocks as 1/4 effective speeds for some cards. In any case, the values displayed on the overclocking applications are correct, so do NOT just set the clocks too high without slowly testing.

Testing
Now that you have found your maximum safe overclock, you need to ensure your card’s stability and operating temperatures. First, open nTune Monitor to display your graphics card’s temperature and set up the log to run. This is to ensure that you have still have temperature data in case your system does crash or reboot. Now, run rthdribl (found on the application list link above) for 2-8hrs. This simple program will stress your graphics card but should not cause any problems to your system even after 8hrs. The next program that should be run is ATITool. In the application, select “Scan for Artifacts” and allow this to run for an hour. After an hour, the clock above the spinning fuzzy cube should match the clock under the cube. The bottom clock tells how long the test has been performed without detecting a graphical error (artifact). If the two timers do not match, go back to nTune or RivaTuner (which ever you used) and turn down the overclocks by a bit more. Then repeat the test. Another note, ATITool is quite sensitive so you may want to select mid-level artifact sensitivity under its options. Finally, the last test the needs to be run is 3DMark06. Install the free version and run it at the default settings. The program will provide you a benchmark to compare scores against other similar systems. To improve your score, be sure to have recently defragmented your hard drives and close all other background tasks (except for nTune Monitor for now). Also, the 3DMark scores can fluctuate 50-100 points between runs. During the entire testing process, ensure that your graphics card temperature never breaks 90C (while up to 100C is safe for the 8-series).
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post #4 of 5
Thread Starter 
feck me! that was fast. Going to do all of that DuckieHo as it seems like a concrete way of testing, which is what i'd do with the CPU. I use a variety of programs and benchs for testing my CPU clocks, so I suppose the same should be true for my GPU.

What about voltages though? With my CPU when I hit a barrier I just up the voltage, monitor the temps and move on. Will there be much need to increase teh GPUs volts? Can this be done through the BIOS? Or do I need to short circuit some resistors on the PCB? (i've got a conductive ink pen and i'm not afraid to use it )
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post #5 of 5
Quote:
Originally Posted by leimrod View Post
feck me! that was fast. Going to do all of that DuckieHo as it seems like a concrete way of testing, which is what i'd do with the CPU. I use a variety of programs and benchs for testing my CPU clocks, so I suppose the same should be true for my GPU.

What about voltages though? With my CPU when I hit a barrier I just up the voltage, monitor the temps and move on. Will there be much need to increase teh GPUs volts? Can this be done through the BIOS? Or do I need to short circuit some resistors on the PCB? (i've got a conductive ink pen and i'm not afraid to use it )
The 7900GTX G71 core already has a decent amount of voltage going to it. A 7900GT is more accepting to voltmods because it uses an undervolted G71. You can up the voltage via though the BIOS... however, you will need a custom BIOS to flash the card. Here's a link to 7900GTX v-mods via physical PCB changes:
http://sg.vr-zone.com/?i=3330&s=3
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