Having installed the graphics card on our mainboard, we found the latter to be unable to start up. The BIOS was initialized so we could even enter its interface, but after that we could see nothing but “0_” on a black screen. We solved the problem by using another BIOS. There were as many as five versions for the ASUS ROG Matrix 7970 at www.techpowerup.com and we chose this one. This must have been a compatibility issue between the graphics card and the Intel Siler DX79SR mainboard, but our solution may help someone else.
Before we proceed to testing the graphics card’s overclocking potential, we want to tell you about the exclusive GPU Tweak utility. Unlike MSI Afterburner, it can be used to monitor and tweak any graphics card parameters. Besides clock rates, you can change three voltages:
You can change the speed of each fan individually, specify a Power Target, and increase Load Line Calibration and VRM frequency parameters.
Of course, each of these and many other parameters can be monitored in the utility’s other window, which is very convenient.
GPU Tweak overclocks the GPU in an unusual way. For example, when we increased the GPU clock rate to 1200 MHz on our ASUS ROG Matrix 7970, the utility automatically changed its voltage, into 1.319 volts in our case:
Then, if the GPU clock rate is increased to 1250 MHz, the voltage is set at 1.345 volts:
At 1340 MHz, the voltage is as high as 1.4 volts:
The correlation between frequency and voltage can be disabled in the utility’s settings, but we first tried to use the default ones. This approach wasn’t successful, though. The graphics card would pass our tests, but showed visual artifacts. So, we had to rely on our traditional method and find the highest stable clock rates without any voltage modification. At its default voltage the GPU was stable at 1160 MHz and the graphics memory at 7080 MHz.
Increasing the GPU voltage to 1.3 volts helped raise the clock rate to 1220 MHz only, so we gave up further attempts to overclock at higher voltages. We may have been unlucky or maybe the card really needed even more voltage. Tweaking the VDDCI parameter didn't help, either. After increasing the memory voltage to 1.7 volts we reached 7340 MHz without any stability issues or image artifacts.
The card’s temperature didn’t change much when we overclocked it to 1160/7080 MHz without increasing its voltages. The GPU grew 3°C hotter and the fans sped up by 180 RPM.
Overclocked to 1220/7340 MHz with increased voltage, the GPU would get as hot as 78°C. The cooler’s fans rotated at 2600 RPM.