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NVIDIA has officially killed off 3- and 4-way SLI on its new Pascal GPUs

By Koh Wanzi - on 13 Jun 2016, 4:20pm

NVIDIA has officially killed off 3- and 4-way SLI on its new Pascal GPUs

NVIDIA SLI Pacal

NVIDIA has confirmed that it will focus only on 2-way SLI configurations with its new Pascal GPUs.

While the company originally made clear its focus on 2-way SLI when it launched its GeForce GTX 10-series cards, it said that it would still be making available an Enthusiast Key for hardcore enthusiasts to enable 3- and 4-way setups anyway. But with its decision to abandon the Enthusiast Keys as well, it looks like all roads to more extreme SLI configurations are closed.

The reason behind this is that NVIDIA doesn’t recommend going beyond 2-way SLI, because it has become increasingly difficult to achieve meaningful performance scaling improvements beyond two cards. For instance, a CPU bottleneck is apt to arise in many games as it tries to manage more than two graphics cards.

Furthermore, Pascal cards were originally built to support 2-way SLI. NVIDIA also introduced a new type of high-bandwidth SLI bridges dubbed SLI HB that enabled the interface to run at 650MHz, faster than the 400MHz on older bridges.

NVIDIA GeForce GTX 1080

The new SLI implementation even doubles the bandwidth between GPUs over the older interface. In practice, this means that gamers will be able to squeeze out even more performance from 2-way configurations, especially at ultra-high resolutions or refresh rates exceeding 120Hz. For an idea of how much additional performance to expect, you can check out our preview articles for the GeForce GTX 1070 and 1080 in SLI.

In an emailed statement to PC Perspective, NVIDIA said, “To ensure the best possible gaming experience on our GeForce 10-series GPUs, we’re focusing our efforts on 2-way SLI only and will continue to include 2-way SLI profiles in our Game Ready Drivers.”

However, things are slightly more complicated than that. DirectX 12 adds new multi-GPU modes – multi display adapter (MDA) mode and linked display adapter (LDA) mode. Ashes of the Singularity utilizes MDA mode, which is capable of using any GPU – regardless of manufacturer – in the system. That was why we had to disable SLI in the NVIDIA Control Panel when we were benchmarking 2-way SLI and enable an in-game option to take advantage of multiple GPUs instead.

On the other hand, LDA mode can be subdivided into two further types, namely, implicit and explicit. Unlike MDA mode, this mode requires both GPUs to be similar, and links the GPUs’ memory together to form a large resource pool for the developer. NVIDIA uses implicit LDA for SLI, but explicit mode, along with MDA mode, actually allow game developers to shoulder the responsibility for multi-GPU operation.

What this means is that developers could still theoretically code their games to take advantage of 3- and 4-way configurations, leaving just a sliver of a doorway for those bent on utilizing more than two GPUs. Having said that, we wouldn’t count on this happening too often.

There's just one exception – benchmarks. NVIDIA will enable 3- and 4-way SLI in future drivers without any need for an Enthusiast Key, but only benchmarking applications like 3DMark, Unigine, and Catzilla will be supported.

Source: PC Perspective

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