The GTX 770 arrives to Challenge the HD 7970 GHz Edition – 25 Games benchmarked!

Architecture and Features

We have covered Fermi’s GF100 architecture in a lot of detail previously. You can can read our articles here and also in our coverage of NVIDIA’s GPU Tecnology Conference 2010 that we reported on it for you here, here and here in a three-part series. The Kepler architecture builds on Fermi architecture with some important improvements and refinements.

SMX architecture

As Nvidia’s slide indicates, the Kepler architecture is called SMX and it emphasizes 2x the performance per Watt of Fermi. Their multi-threaded engine handles all of the information using four graphics processing clusters including the raster engine and two streaming multi-processors.

The SM is now called the SMX cluster. Each SMX cluster includes a Polymorph 2.0 engine, 192 CUDA cores, 16 texture units and a lot of high-level cache. To add it all up, 2 SMXs each times 16 SMXs each including 192 CUDA cores, equal 1536 CUDA cores in the GPU used for the GTX 680 and the GTX 770.

Four raster units and 128 Texture units comprise 32 ROPs; eight geometry units each have a tessellation unit, and more lower-level cache.

Nvidia significantly improved their memory controller over the Fermi generation as the GTX 680 uses a 256-bit wide GDDR5 memory interface at 6Gbps declared throughput.

The GTX 770 takes it further to increase the bandwidth by using the world’s first 7Gbps GDDR5 as increasing the GTX 770’s core speed without increasing the memory would starve the core.  Peak memory bandwidth is 224.3GB/sec – that’s about 15% more memory bandwidth than last year’s GTX 680.

The above is a very brief overview of Kepler architecture as presented to the press at Kepler Editor’s Day in San Francisco last year.

Adaptive VSync

Traditional VSync is great for eliminating tearing until the frame rate drops below the target – then there is a severe drop from usually 60 fps down to 30 fps if it cannot meet exactly 60. When that happens, there is a noticeable stutter.

Nvidia’s solution is to dynamically adjust VSync – to turn it on and off instantaneously. In this way VSync continues to prevent tearing but when it drops below 60 fps, it shuts off VSync to reduce stuttering instead of drastically dropping frame rates from 60 to 30 fps or even lower. When the minimum target is again met, VSync kicks back in. In gaming, you never notice Adaptive VSync is happening; you just notice less stutter (in demanding games, especially).

Adaptive VSync is a good solution that works well in practice.

Specifications

Here are the specifications for the GTX 680:

Now let’s look at the GTX 770 specifications.  Remember, however, the GTX 770 at $399 is replacing the GTX 670 which also launched at $399, not the (currently, $450) GTX 680 which is being replaced by the ($650) GTX 780.

First, we notice that everything is identical between the GTX 770 and the GTX 680 except for the increased memory speed plus the increased base core speed, from 1006MHz of the GTX 680 to 1046MHz of the GTX 770. We note that the original Boost of the GTX 680 has been increased also and replaced with the improved Boost 2 of the 700 series.  The TDP of the GTX 680 GPU has gone up from 195W of the GTX 680 to 230W for the GTX 770 which now requires 6+8 pin PCIe power connectors instead of the 6+6 pin PCIe connectors used for the GTX 680.

Let’s take a closer look at the GTX 770.