AMD Radeon 660M vs NVIDIA GeForce GTX 960M vs NVIDIA GeForce GTX 980M SLI

AMD Radeon 660M

The AMD Radeon 660M is an integrated GPU in the entry level Ryzen 6000 series for laptops (Rembrandt, e.g. Ryzen 5 6600U). The GPU is based on the RDNA2 architecture and has 6 of the 12 CUs (= 384 shaders) clocked at up to 1,900 MHz (depending on the CPU model). The 680M and 660M iGPUs are the first integrated graphics card with hardware raytracing support, although the performance is too slow to use it in current games.

Due to the halved CU count and lower core clock, the Radeon 660M is clearly slower than the Radeon 680M and most likely only on par with the old Radeon Vega 8 iGPUs. 

Thanks to the modern 6nm process and clever power-saving features, the power consumption is comparatively low (according to AMD), so the graphics card can also be used for slim and light notebooks (depending on the CPU model).

NVIDIA GeForce GTX 960M

The NVIDIA GeForce GTX 960M is an upper mid-range, DirectX 11-compatible graphics card for laptops unveiled in March 2015. It is based on Nvidia's Maxwell architecture (GM107 chip) and manufactured in 28 nm. The GTX 960M offers 640 shader units clocked at 1097 - 1202 MHz (Boost) as well as fast GDDR5 memory (128 bit, 5000 MHz effective, 80 GB/s).

Compared to the previous and technically very similar GTX 860M, the GTX 960M is clocked slightly higher.

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 increased size can handle some of the memory traffic to allow for a relatively narrow memory interface without significantly reducing the performance.

GM107 supports DirectX 12 with feature level 11_0 only.

Performance

Although the GTX 960M has the same memory bandwidth as the previous GTX 860M, its higher core clock leads to a slightly better performance. Overall, the 960M is almost 10 percent faster and similar to the desktop GTX 750 Ti.

Many games of 2014/2015 can be played fluently in FullHD resolution and high detail settings. However, very demanding games such as Assassin's Creed Unity 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 960M should be similar to the old GTX 860M (about 60 watts). Therefore, the GPU is best suited for 15-inch laptops or larger. The 900M series also supports Optimus to automatically switch between an integrated graphics card and the Nvidia GPU.

NVIDIA GeForce GTX 980M SLI

The NVIDIA GeForce GTX 980M SLI is a high-end DirectX 11-compatible graphics solution for laptops, consisting of two GeForce GTX 980M. Each card has a 28 nm GM204 GPU based on the Maxwell architecture, which is the same chip as found on the GTX 970M as well as several desktop cards. The clocks for the SLI-setup are usually identical to a single GTX 980M (1038 MHz GPU, 1250 MHz memory).

With SLI, each card renders a single frame (AFR mode). Therefore, it may suffer from micro stuttering in low fps ranges of 30 fps. This happens because of different timespans between two frames (e.g., irregular delays between sequential frames).

Architecture

GM204 is based on Nvidia's Maxwell architecture, which replaces the previous Kepler generation. Among other changes, Nvidia have restructured the streaming multi processors (SMM) in order to increase workload and efficiency. Now each SMM contains only 128 shader units and 8 TMUs, which is noticeably less than an equivalent Kepler GPU. The GM204 features four GPCs, and each consists of four SMMs. But, in the GeForce GTX 980M, Nvidia have deactivated 4 of 16 SMMs. As a result, only 1536 shader ALUs and 96 TMUs are active. In addition, there are 64 ROPs in four clusters with 16 units each.

The memory interface has a bandwidth of 256-bits (4x 64 bit) for each of the two GPUs. Thanks to an improved compression algorithm, the connection to the GDDR5 memory should be significantly more efficient per MHz. Furthermore, the L1 (96 KB per SMM) and L2 caches (2 MB) have been significantly increased to lower the needed bandwidth. Compared to the mid-range GM107, the newer and larger GM204 has several additional features and changes. Aside from the improved polymorphic engine in the SSMs, it is also the first Nvidia chip to support DirectX 12 Feature Level 12_1.

Performance

With good driver support, SLI almost doubles the performance of a single card. The GTX 980M SLI outperforms the GeForce GTX 970M SLI by about 30 percent and is the fastest mobile graphics solution in late 2014. Compared to the former GTX 880M SLI, the advantage is even bigger (40 - 50 percent). Thus, the GTX 980M SLI is powerful enough to run even the most demanding games with highest details, AA/AF and resolutions exceeding FullHD.

Features

Most of the features are identical to the GeForce GTX 800M series. With the GTX 980M, there can be up to 4 active displays possible, but this will likely decrease due to Optimus. Displays can be connected with a maximum resolution of 3840 x 2160 pixels via DisplayPort 1.2 or HDMI 2.0 (no HDCP @ 4K). HD audio formats like Dolby True HD and DTS HD can be sent to a compatible receiver as bitstream. As with previous models, 3D Vision is not supported with Optimus.

The updated video processor VP6 supports the usual formats like H.264 and can also decode and encode H.265 with a resolution of up to 4K via the NVENC API. Several parallel streams, such as picture-in-picture in a Blu-Ray movie, are also possible.

Further features of the GTX 900M series, which are also partly supported by older cards, include Battery Boost (longer battery life during gaming), Shadowplay (recording of gaming videos up to 4K60p and 130 Mbit/s) and Gamestream (game streaming on Shield console). More information on these features are available here.

Power Consumption

The power consumption of each GeForce GTX 980M including its MXM board and memory should be about the same as a GTX 880M with a specified TDP of 122 W, leading to a total TDP of about 240 W. Given the significantly higher performance, this can be considered a massive increase in performance-per-watt. Nevertheless, the SLI setup can only be used in very large and heavy gaming notebooks with powerful cooling systems. Under low load, dynamic clock rates help the GPUs to save energy.