NVIDIA GeForce 845M vs NVIDIA GeForce GTX 760M

NVIDIA GeForce 845M

The NVIDIA GeForce 845M is a mid-range, DirectX 12-compatible graphics card for laptops unveiled in spring 2014. It is one of the first cards based on Nvidia's new Maxwell architecture, but is still manufactured in 28 nm. In addition to a version based on GM107 (partially deactivated to 384 ALUs, 128-bit, DDR3 memory), there is also another version using the GM108 chip (384 Shader, 64-bit, GDDR5 memory). Both models offer approximately the same performance.

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.

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, the GM107 and GM108 support DirectX 12 with feature level 11.0 only.

Performance

Thanks to the 128-bit memory interface (respectively the GDDR5 memory of the GM108 model), the GeForce 845M offers about 30 percent more performance than the GeForce 840M. However, a GeForce GTX 850M is still an additional 50 percent faster. Many games of 2013/2014 (Tomb Raider or BioShock Infinite, etc.) can be played fluently in 1366 x 768 and high detail settings. Very demanding games such as Crysis 3 or Battlefield 4 will require lower resolutions and/or details.

Features

GM107/108 integrate 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 845M should be in a range of about 30 - 35 Watts. Therefore, the card is best suited for 14-inch laptops or larger. The 800M series also supports Optimus to automatically switch between an integrated graphics card and the Nvidia GPU.

NVIDIA GeForce GTX 760M

The NVIDIA GeForce GTX 760M is a upper mid-range DirectX 11-compatible graphics card for laptops. In contrast to the GTX 660M, the 760M now uses the GK106 chip and offers twice the amount of shaders at a slightly reduced core speed. However, the memory bus is still only 128 Bit wide.

As a novelty, the GeForce 700M series implements GPU Boost 2.0 to automatically overclock the core clock rate. Depending on the cooling headroom of the laptop and the application / game, 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 GK106 Kepler core offers five shader blocks, called SMX, that are clocked at the same speed as the central core. In the GTX 760M, four blocks are active for a total of 768 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 760M is clearly above the GTX 660M thanks to the higher amount of shaders. Depending on the GPU Boost 2.0 up to 30 % better performance can be achieved (according to Nvidia).

In our tests with a quad-core of the Haswell generation, the GTX 760M performs on par with a GTX 670M or Radeon HD 8870M. In demanding games like Crysis 3, BioShock Infinite or Hitman: Absolution the GTX760M is able to achieve good framerates in high details and 1366x768 pixels. Less demanding games like Dead Space 3, Modern Warfare 3 or Deus Ex Human Revolution were even playable in Full HD and maximum details.

Features
The feature set of the GTX760M is identical to the GTX670MX as both are based on the same GK106 core. Therefore the GPU supports 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. Finally, the dedicated video encoding engine called NVENC API similar to Intel QuickSync is integrated in the chip.

The power consumption of the GeForce GTX 760M should be similar to the GTX 660M (50W) and is therefore best suited for large notebooks (15-inches or greater) and desktop replacements.