Just like AMD hit a power wall with the R600 (HD 2900), NVIDIA had the same experience with the first Fermi, i.e. the GeForce GTX 480. AMD's answer to power inefficiencies was Radeon HD 3870 and later, HD 4870 - power efficient GPUs which took the best parts of R600 architecture and combined it with fixed function parts, getting nice, power efficient products.
With Kepler, took a similar approach - take what is good from Fermi and throw out everything else. NVIDIA had enough time to completely reorganize the way how the GPU works. When designing Kepler, the company architects decided to reduce the power as much as possible, and the decision was made to abandon the "double-pumped", "hot clocks" concept. New concept increased the needed die area for physical cores and reduced the power consumption. The cores used the same physical space, but at half the power.
With the excessive control logic thrown out, enough room opened not to just double the core count, but rather triple it. While NVIDIA was making this chip, its designation was "performance" and the target positioning was "GeForce GTX 670 Ti". However, after the company received first 28nm silicon back, the triple core count worked better than expected and enabled engineers to clock the parts higher than expected. At the same time, the new software-driven approach resulted in reduced complexity and easier performance tuning. As such, the part planned as GTX 670 Titanium became the GTX 680.Kepler's power efficiency - On avergage 30-50% more efficient than Fermi
In real world applications, GK104 was twice as efficient as GF110 in Battlefied 3, with other applications following suit. Worst efficiency was achieved in The Elder Scrolls V: Skyrim and Batman: Arkham City. On average, Kepler is between 30-50% more power efficient than the Fermi architecture.
The real efficiency is seen when you take a look at the notebook part. The GK107 packs 384 cores and that was enough to GPU Boost
When your silicon is power efficient, an interesting thing happens - you can clock it to heavens high and beat your competition on clock, should logic lack the sophistication. If you end with sophisticated logic and low power consumption, you have a brilliant chance of taking the market.
In NVIDIA, the "holy duality" effect happened with Riva TNT2, GeForce 4 Titanium, GeForce 6000, 7000 Series and now with the GeForce GTX 600 Series. In our conversations, we learned that NVIDIA always planned to launch the GPU Boost feature, but they weren't certain just how good the boost can be. GPU Boost is similar to Turbo mode on CPUs of today with several changes. Turbo mode on modern processors works that algorithm checks for current load of the cores, actual temperature and power consumption. Based on the information given, the Turbo mode will clock one or two cores to the Maximum TDP, or clock all available cores until maximum power consumption is reached.
Given that it controls the whole board, GPU Boost is far more complex system. The system works with the algorithm checking the actual GPU and RAM power consumption, utilization, GPU temperature and similar parts of the board. End result is that the GPU Boost will not just change frequency of a single core (it does not make lot of sense with the way how GPU works), but rather increase the frequency of both the GPU and on-board memory. Furthermore, GPU and memory voltage will be increased to the safe point, i.e. maximum power consumption. NVIDIA stated that the GeForce GTX 680 has two 6-pin connectors and can take a maximum of 225W, 75W less than GTX 580. We have no doubt that custom GTX 680 boards will bring 8+6-pin configuration (300W) for maximum performance.
GPU Boost doesn't stop with the set TDP, though. Overclocking is favorite past time for a lot of engineers (and users) and NVIDIA utilized GPU Boost to enable board partners to overclock their parts based on better cooling (read: parts with the most efficient cooling will have more headroom by default BIOS settings, yet alone after vendor-specific BIOS tweaks).
When overclocking the GPU, GPU Boost will continue to run in the background, and if you bin the GPU/DRAM chips, you might end up with a monster. In our testing, we've found that GPU Boost works quite impressive, with the maximum clock achieved being 1,316 MHz - over 30% from default 1008 MHz. The clock was good enough to beat a GeForce GTX 590, which is based on two Fermi GPUs.GPU Boost also plays a very important role in notebook design
Beside the desktop part, GPU Boost is also used in the notebooks. The algorithm looks at the whole computer and tries to redirect each available Watt of power to the GPU, increasing performance by quite a bit. While 5W of power doesn't mean a lot in desktop world, we're talking about one fourth of the overall power budget for the Ultrabook/Notebook part, resulting in higher performance.
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