NVIDIA GeForce GTX 770M SLI vs NVIDIA GeForce GTX 780M SLI

NVIDIA GeForce GTX 770M SLI

The NVIDIA GeForce GTX 770M SLI is a high-end DirectX 11-compatible graphics solution for laptops, consisting of two GeForce GTX 770M. Each card has a 28nm GK106 core based on the Kepler architecture. The clocks for the SLI-setup are identical to a single GTX 770M. With SLI, each card usually renders a single frame (AFR mode). Therefore, it may suffer from micro stuttering in low fps ranges of 30fps. This happens because of different timespans between two frames (e.g., irregular delays between sequential frames).

Architecture

The Kepler architecture is the successor to the Fermi architecture that first appeared in laptops with the GeForce 400M series. The GK106 Kepler core offers five shader blocks, called SMX, that are clocked at the same speed as the central core. In the GTX 770M, all five blocks are activated (= 960 CUDA-Cores for each 770M). Although the Kepler architecture can utilize more shader cores than a Fermi chip, its shaders can be up to twice as power efficient. However, due to the missing hot clock of the shader domain, two shaders of a Kepler chip are of similar speed to one shader of a Fermi chip (as the latter is clocked twice as fast).

PCIe 3.0 is now supported by the mobile Kepler series and GPU Boost 2.0 can automatically overclock the card if the laptop cooling system allows it. This feature is available on any notebook with a graphics card of the 700M series.

Performance

The GeForce GTX 770M SLI is about 70 - 80 percent faster than a single GTX 770M, leading to a performance somewhere between a single GeForce GTX 680 (desktop) and GTX 780M. Therefore, most games (as of 2013) are playable at the highest detail setting and in FullHD resolution. In many cases it is even possible to activate additional anti-aliasing.

Features

The feature set includes support for up to 4 active displays. Furthermore, high resolution monitors of up to 3840x2160 pixels can now be connected using DisplayPort 1.2 or HDMI 1.4a if available. HD-Audio codecs, such as Dolby TrueHD and DTS-HD, can be transmitted via bitstream mode through the HDMI port. However, as most laptops will feature Optimus, the integrated GPU will likely have direct control over the display ports and may limit the feature set available by the Nvidia Kepler cards.

The 5th generation PureVideo HD video processor (VP5) is also integrated in the GK106 core and offers hardware decoding of HD videos. Common codecs such as MPEG-1/2, MPEG-4 ASP, H.264 and VC1/WMV9 are fully supported up to 4K resolutions while VC1 and MPEG-4 are supported up to 1080p. Two streams can be decoded in parallel for features such as Picture-in-Picture. Another novelty is the inclusion of a dedicated video encoding engine similar to Intel QuickSync that can be accessed by the NVENC API.

Power consumption

The power consumption of the GeForce GTX 770M SLI should double to about 150 watts (including board and memory) compared to a single GTX 770M. Therefore, only large desktop replacements can handle the heat.

NVIDIA GeForce GTX 780M SLI

The NVIDIA GeForce GTX 780M SLI is a high-end DirectX 11-compatible graphics card for laptops, consisting of two GeForce GTX 780M. Each card has a 28nm GK104 core based on the Kepler architecture. The clocks for the SLI-setup are in theory identical to a single GTX 780M. With SLI, each card usually renders a single frame (AFR mode). Therefore, it may suffer from micro stuttering in low fps ranges of 30fps. This happens because of different timespans between two frames (e.g., irregular delays between sequential frames).

Architecture
The Kepler architecture is the successor to the Fermi architecture that first appeared in laptops with the GeForce 400M series. The GK104 Kepler core offers eight shader blocks, called SMX, that are clocked at the same speed as the central core. In the GTX 780M, all eight blocks are active for a total of 1536 CUDA cores. Although the Kepler architecture can utilize more shader cores than a Fermi chip, its shaders can be up to twice as power efficient.  However, due to the missing hot clock of the shader domain, two shaders of a Kepler chip are of similar speed to one shader of a Fermi chip (as the latter is clocked twice as fast).

PCIe 3.0 is now supported by the mobile Kepler series and an optional Turbo mode can automatically overclock the Nvidia card by a theoretical 15 percent if the laptop cooling system allows it. The implementation of this boost mode is done in the BIOS, but it is ultimately dependent upon the manufacturer of the laptop.

Performance

The graphics performance of the GeForce GTX 780M SLI is clearly above the old GTX 680M SLI and Radeon HD 7970M Crossfire (or 8970M CF), thus making it the fastest mobile solution as of summer 2013. Furthermore, Nvidia currently (mid 2013) has a better mechanism to minimize micro stuttering (altough not perfect).

Even extremely demanding titles like Metro Last Light or Crysis 3 are playable at the highest detail settings in 1920x1080 pixels and anti aliasing.

Features
The improved feature set now includes support for up to 4 active displays. Furthermore, high resolution monitors of up to 3840x2160 pixels can now be connected using DisplayPort 1.2 or HDMI 1.4a if available. HD-Audio codecs, such as Dolby TrueHD and DTS-HD, can be transmitted via bitstream mode through the HDMI port. However, as most laptops will feature Optimus, the integrated GPU will likely have direct control over the display ports and may limit the feature set available by the Nvidia Kepler cards.

The 5th generation PureVideo HD video processor (VP5) is also integrated in the GK104 core and offers hardware decoding of HD videos. Common codecs such as MPEG-1/2, MPEG-4 ASP, H.264 and VC1/WMV9 are fully supported up to 4K resolutions while VC1 and MPEG-4 are supported up to 1080p. Two streams can be decoded in parallel for features such as Picture-in-Picture. Another novelty is the inclusion of a dedicated video encoding engine similar to Intel QuickSync that can be accessed by the NVENC API.

The power consumption of the GeForce GTX 780M SLI should double to 200 Watt (including board and memory) compared to a single GTX 780M. Therefore, only large desktop replacements can handle the heat.