NVIDIA GeForce GTX 780 Review

Author: SKYMTL
Date: May 21, 2013
Product Name: GTX 780 3GB
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Kepler’s Overclocking: Overhauled & Over-Volted

One of the major criticisms leveled at the early Kepler cards like the GTX 680 was their bewildering lack of core voltage control. Some board partners eventually added the capability to modify their cards’ voltage values but they were quickly removed in favor of a supposedly “safer” approach to overclocking. Enthusiasts weren’t happy and neither were NVIDIA’s partners since they had to eliminate certain advertised features from their products.

With GK110, voltage control is making a return….to a certain extent, and regrettably it won’t cascade down to lower-end SKUs like the GTX 680. NVIDIA will be allowing voltage changes, but the actual upper limits will remain under strict control and could be eliminated altogether on some products should a board partner decide to err on the side of caution.

On the previous page, we detailed how GK110’s Boost Clock is largely determined by a complex calculation which takes into account temperatures, clock speeds, fan speeds, Power Target and core voltage. As temperatures hit a given point, Boost 2.0 will adapt performance and voltage in an effort to remain at a constant thermal point. This methodology remains in place when using GK110’s expanded overclocking suite. However, in this case, the application of additional voltage will give Boost another “gear” so to speak, allowing for higher clock speeds than would normally be achieved.

Since Over Voltage control falls under the auspices of GPU Boost 2.0, the associated limitations regarding thermal limits and their relation to final in-game clock speeds remain in place. Increasing voltage will of course have a negative impact upon thermal load which could lead to Boost throttling performance back until an acceptable temperature is achieved. Therefore, even when a voltage increase is combined with a higher Power Limit and GPU Clock Offset, an overclock may still be artificially limited by the software’s iron clad grip unless temperatures are reigned in. This is why you’ll likely want to look at improving cooling performance before assuming an overclock will yield better results or, while not recommended, expand the Temperature Target to somewhere above the default 80°C mark.

GTX TITAN’s maximum default voltage is currently set roughly 1.125V which results in clock speeds that (in our case at least) run up to the 940MHz mark, provided there is sufficient thermal overhead. EVGA’s Precision tool meanwhile allows this to be bumped up to by a mere .035V which likely won’t result in a huge amount of additional overclocking headroom. However, while the maximum Boost clock may not be significantly impacted by the additional voltage, it should allow the GTX 780 to reach higher average speeds more often, thus improving overall performance. Also expect other board partners to have different maximum voltages set in their VBIOS.

In order to put NVIDIA’s new voltage controls to the test, we ran the GTX 780 at default clock speeds (GPU and Memory offsets were pegged at “0”) with the Power Target set to 106% and keeping the core temperature at a constant 75°C versus a Temp Target of 80°C. In practice, this should allow that extra .035V to push the maximum Boost speed to another level.

While the frequency increase we’re seeing here is rather anemic, NVIDIA’s inclusion of limited control over core voltage should be welcomed with open arms. Regardless of the end result, seeing a card like the GTX 780 operating above 1GHz is quite impressive. Some enthusiasts will likely throw their noses up at the severe handicap placed upon the maximum allowable limits but any more could negatively impact ASIC longevity.

In addition, don’t expect the same support from every board partner since NVIDIA hasn’t made the inclusion of voltage control mandatory, nor is the maximum voltage set in stone. Some manufacturers may simply decide to forego the inclusion of voltage modifiers within their VBIOS, eliminating this feature altogether.

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