Let’s check out the efficiency of Nvidia’s multi-GPU technology first. Here’s the 2-way SLI tandem compared to the single GeForce GTX 780 Ti at the same clock rates:
Depending on the resolution and visual quality settings, adding a second GeForce GTX 780 Ti card may ensure a performance boost up to 90%, if the game is supported properly by the graphics driver. So when everything works smoothly, the performance gain is almost twofold. On the other hand, there are cases where the SLI technology is inefficient or doesn’t work at all. It depends on the particular game whether building such a tandem is worthwhile.
Next, we compare the two GeForce GTX 780 Ti cards with the dual-processor GeForce GTX 690. Both use the same driver and SLI technology.
Except for a few games, the 2-way GeForce GTX 780 Ti SLI is much faster than the GeForce GTX 690. The average gap is 48% at the high visual quality settings.
The SLI tandem is also an average 56% ahead of the AMD Radeon HD 7990 at the same settings:
The SLI configuration loses a couple of tests either because the game is limited by the speed of the platform (Hitman: Absolution) or doesn’t work smoothly with SLI (Battlefield 4). Overall, the 2-way GeForce GTX 780 Ti SLI enjoys a larger advantage over the AMD Radeon HD 7990 than over the GeForce GTX 690.
We measured the power consumption of computer systems with different graphics cards using a multifunctional panel Zalman ZM-MFC3 which can report how much power a computer (the monitor not included) draws from a wall socket. There were two test modes: 2D (editing documents in Microsoft Word and web surfing) and 3D (the intro scene of the Swamp level from Crysis 3 running four times in a loop at 2560x1440 with maximum visual quality settings but without MSAA). Here are the results:
The computer with our 2-way GeForce GTX 780 Ti SLI configuration needs about 800 watts of power at peak loads, so you’d need at least a 850W PSU for it. This is 116 watts more than required by the computer with an overclocked AMD Radeon HD 7990. The Nvidia GeForce GTX 690 system needs 144 watts less and the system with one GeForce GTX 780 Ti (working at the same clock rates) needs 217 watts less.
A SLI tandem built out of two GeForce GTX 780 Ti cards is one of the fastest graphics subsystems available today and is perfect for the most resource-consuming games and benchmarks. It will cost you about as much money as a whole midrange PC but its graphics performance is going to be unprecedented. It is only necessary for the game to support SLI technology and for the Nvidia GeForce driver to have appropriate optimizations. Of course, as is always the case with products of such a high class, you need a high-performance platform, a high-wattage PSU and a roomy computer case. In the best scenario, the two GeForce GTX 780 Ti will almost double the frame rate of a single such card. Crysis 3, Metro: Last Light and Tomb Raider indicate that such an advanced graphics subsystem won’t be overkill. So if you can afford a couple of GTX 780 Ti cards and prefer premium-quality graphics, you should certainly try combining them into a 2-way SLI tandem.