The Khronos Group presented new information and slides about Vulkan API developments back at GDC 2017, a couple of weeks ago. As a DirectX 12 competitor in the game development space on Windows systems many Windows 7 and 8.1 diehards hope the Vulkan API will bring DX12 style modern multi-core multi-thread hardware support without the need to migrate to Windows 10. However, as DSO Gaming has reported, Vulkan looks like it will need Windows 10 for at least one major feature - native multi-GPU support for Nvidia SLI and AMD Crossfire platforms.
The above news is of concern only to Windows OS users, notes the source. Linux PC gamers using Vulkan aren't going to be restricted in the same way.
According to the Khronos Group's Vulkan presentation slides from GDC, the restrictions on Windows OS users is down to the fact that for Nvidia SLI or AMD CrossFire the "WDDM must be in 'linked display adapter' mode." This is a mode only supported in the new Windows 10 WDDM 2.0, an exclusive to the OS. Thus it looks like Vulkan gamers using Windows 7 or 8.1 will be restricted to single GPU usage for the foreseeable future.
The next bullet point also highlights a restriction. It says that Vulkan won't commonly support multi-GPU on systems with mixed discrete and integrated graphics. That applies to Windows 10 users too.
Game developers have to work to add support for multi-GPU manually which means it isn't a very common feature in games and apps right now.
Khronos has contacted HEXUS to say that "It is possible to implement Vulkan multi-GPU extension on any desktop OS including Windows 7, 8.X, 10, and Linux." In other words, multi-GPU usage in the Vulkan API is "not tied to Windows 10".
Due to the deluge of similar news about Windows 10, multi-GPU, and Vulkan - all emanating from the official slide at the top of this article, Khronos has published a blog post which seeks to clear things up.If you are interested in the details click through and read 'Vulkan Multi-GPU Support - Not Just for Windows 10'.