Overclocking a GTX 780 usually boils down to increasing clock speeds, maxing out the pitiful voltage and Power Limit sliders and then smashing face first into NVIDIA’s predetermined ceiling. It was an infinitely frustrating process that dragged down even the most expensive cards. The challenges were of course multi faceted: on one hand there’s a Voltage Limit which can only be increase by a pitiful 38mV. If that helps out, the Power Limit will usually step in and cap clock speeds since higher voltage typically leads to greater core power needs. It goes without saying that NVIDIA’s maximum of 110% simply isn’t enough.
As we mentioned in the introduction, EVGA’s community of intrepid overclockers has found a number of ways around these hurdles. May of these community developed tools we’ll be discussing can be found in this thread over at Overclock.net. Basically, any GTX 780 Classified experience (not to mention review) would be incomplete without delving into the finer points of pushing past NVIDIA’s barriers.
The cornerstone of EVGA’s overclocking suite is their Precision tool, a utility that continues to evolve and still provides one of the best software monitoring and tuning platforms around. Here, you are able to push the Classified but only within the usual boundaries even though EVGA has kindly provided a preloaded secondary BIOS which allows for a Power Target of 115%.
Unfortunately, this higher Power Target really won’t do all that much simply because the Classified’s clock speeds are held back by NVIDIA’s maximum voltage. This means your overclocks will hit a voltage bottleneck long before the core gets starved for power.
The first step towards overcoming the voltage limitation is to install the aptly-named GTX Classified Tuner. This lightweight tool allows for tuning voltages on the core (NVVDD) memory (FBVDD) and PCI Express (PEXVDD), all items which are typically unlocked with the EVBot. Before delving too far into these, remember that the voltages listed aren’t additive but rather represent the true current going to each of those components.
There is an art to overclocking the Classified since it may be a forgiving card with an unbelievable amount of frequency overhead but its still governed by the laws of GPU engineering. Basically, voltage plus more power equals higher temperatures. The trick is balancing all three in order to get optimal clock speeds. This is where NVIDIA’s Reasons come into play since they tell you exactly what’s holding back a given overclock. Typically, this means maximizing the Power Target and temperatures before moving onto voltage since it will have a drastic impact upon the other two metrics.
Take the picture above for example. In it, we can see the Classified under full load (Unigine Valley running on a second screen) at an incredible and relatively constant 1360MHz.
That’s an achievement worthy of note on air cooling but Precision’s readout tells us both voltage and power are our limiting factors, subsequently dragging down clock speeds. Increasing both leads to increased heat output and that wouldn’t be optimal since the Classified was already running at almost 90°C with the fans set at 85%. Unfortunately, that meant it was time to scale things back a bit.
By moving to a core speed of 1.32GHz, we were able to all but eliminate the ultra high temperatures and ensure a continual clock speed, regardless of the situation. Temperatures normalized as well. After 20 minutes of constant load (see the image above), the core frequency didn’t budge one iota, though we were still hitting the Classified’s Voltage Limit. This goes to show that just a moderate voltage boost could actually reduce clock speeds rather than improve overhead.
Did we forget to mention memory? Well, that topped out at 7426MHz before the GDDR5’s error correction stepped in, which is nothing short of incredible.
EVGA has obviously created a monster and unlike its competition, the Classified has the tools necessary to push the very limits of Kepler overclocking. Granted, we were held back by temperatures even without resorting to the custom BIOS which grants a Power Target of 200% but with better cooling, the sky’s the limit.
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