NVIDIA GeForce GTX 770M SLI vs NVIDIA GeForce GTX 775M

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 775M

The NVIDIA GeForce GTX 775M is a high-end DirectX 11-compatible graphics card for laptops. Just like the GTX 780M, it is based on the 28nm GK104 Kepler architecture, but offers less CUDA cores (1344 vs. 1536) and lower clock rates.

As a novelty, the GeForce 700M series implements PCIe 3.0 as well as GPU Boost 2.0 to automatically overclock the core clock rate. Depending on the cooling headroom of the laptop and the application, up to 15 % performance gains are possible.

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 775M, only seven blocks are active for a total of 1344 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).

Performance
The graphics performance of the GeForce GTX 775M should be almost identical to the GTX 680M, making it somewhat faster than the Radeon HD 7970M. The GPU has enough power to run demanding games of 2012 and 2013 fluently with Full HD resolution and maxed out graphical settings. Only extremely demanding titles like The Witcher 2 will not run fluently in ultra settings. Battlefield 3, Skyrim and Crysis 2, for example, are playable at the highest detail settings.

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 775M is rated at a TDP of 100 watts. Therefore, the card therefore is suited for large notebooks (15-17 inches or greater) and desktop replacements.