NVIDIA GeForce GTX 860M SLI vs NVIDIA GeForce GTX 850M

NVIDIA GeForce GTX 860M SLI

The NVIDIA GeForce GTX 860M SLI is a high-end DirectX 12-compatible graphics solution for laptops, consisting of two GeForce GTX 860M. Each card has a 28 nm GM107 core based on the Maxwell architecture. The clocks for the SLI-setup are identical to a single GTX 860M. 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).

Alternatively, there is also a version based on the Kepler chip GK104, which has 1152 shader units clocked at 797 MHz.

Architecture

Compared to Kepler, Maxwell has been optimized in several details to increase power efficiency. Smaller Streaming Multiprocessors (SMM) with only 128 ALUs (Kepler: 192) and an optimized scheduler should lead to better utilization of the shaders. Nvidia promises that a Maxwell SMM with 128 ALUs can offer 90 percent of the performance of a Kepler SMX with 192 ALUs. Each of the two GM107 features 5 SMMs and thus 640 shader cores, 40 TMUs and 16 ROPs (128-bit interface).

Another optimization is the massively enlarged L2 cache (GM107: 2 MB). The increased size can handle some of the memory traffic to allow for a relatively narrow memory interface without significantly reducing the performance.

Similar to Fermi and Kepler, Maxwell / GM107 supports DirectX 12 with feature level 11.0 only.

Performance

The GeForce GTX 860M SLI is about 70 - 80 percent faster than a single GTX 860M, leading to a performance somewhere between a single GeForce GTX 680 (desktop) and Radeon R9 280X (desktop). Accordingly, the 860M SLI competes with the high-end single-GPU GeForce GTX 880M. Most games (as of 2014) are playable at the highest detail setting and in FullHD resolution. In many cases it is even possible to activate additional anti-aliasing.

Features

GM107 integrates the sixth generation of the PureVideo HD video engine (VP6), offering a better decoding performance for H.264 and MPEG-2 videos. Of course, VP6 supports all features of previous generations (4K support, PIP, video encoding via NVENC API). Unfortunately, HDMI 2.0 is still not supported.

Power consumption

The power consumption of the GeForce GTX 860M SLI should double from 60 to about 120 watts (including board and memory) compared to a single GTX 860M. Therefore, only large desktop replacements can handle the heat.

NVIDIA GeForce GTX 850M

The NVIDIA GeForce GTX 850M is an upper mid-range, DirectX 12-compatible graphics card for laptops unveiled in March 2014. It is one of the first cards based on Nvidia's new Maxwell architecture (GM107 chip), but is still manufactured in 28 nm. The GTX 850M offers 640 shader units clocked at 876 MHz (+ Boost) as well as 4 GB of GDDR5 memory (128 bit, 5000 MHz effective). In addition, there is a slightly higher clocked version (936 MHz + Boost) using slower DDR3 memory (2000 MHz effective).

Architecture

Compared to Kepler, Maxwell has been optimized in several details to increase power efficiency. Smaller Streaming Multiprocessors (SMM) with only 128 ALUs (Kepler: 192) and an optimized scheduler should lead to better utilization of the shaders. Nvidia promises that a Maxwell SMM with 128 ALUs can offer 90 percent of the performance of a Kepler SMX with 192 ALUs. GM107 features 5 SMMs and thus 640 shader cores, 40 TMUs and 16 ROPs (128-bit interface).

Another optimization is the massively enlarged L2 cache (GM107: 2 MB). The larger size can process some of the memory traffic to allow for a relatively narrow memory interface without significantly reducing performance.

Similar to Fermi and Kepler, Maxwell / GM107 supports DirectX 12 with feature level 11_0 only.

Performance

Although the GTX 850M has less shaders, it often outperforms the old Kepler-based GeForce GTX 765M while drawing less power. Despite the lower core clock, the GDDR5 version usually takes the lead over the DDR3 model and sometimes even beats the Kepler variant of the GeForce GTX 860M. Many games of 2013/2014 (Tomb Raider or BioShock Infinite, etc.) can be played fluently in FullHD resolution and high detail settings. However, very demanding games such as Crysis 3 or Battlefield 4 will require lower resolutions and/or details.

Features

GM107 integrates the sixth generation of the PureVideo HD video engine (VP6), offering a better decoding performance for H.264 and MPEG-2 videos. Of course, VP6 supports all features of previous generations (4K support, PIP, video encoding via NVENC API). Unfortunately, HDMI 2.0 is still not supported.

Power Consumption

The power consumption of the GeForce GTX 850M should be somewhat below the old GTX 760M at about 40 - 45 Watts. Therefore, the 850M is best suited for 15-inch laptops or larger. The 800M series also supports Optimus to automatically switch between an integrated graphics card and the Nvidia GPU.