Over the last week or so, it has been widely reported that the Vulkan API would not support multi GPU setups on older versions of Windows. This topic came to a head when the studio behind Star Citizen announced plans to drop DirectX 12 in favour of Vulkan due to its multi-OS support. It turns out, those reports were inaccurate, as the Kronos Group has come out this week to explain that the Vulkan API will support SLI/Crossfire on Windows 7/8.1 as well as Windows 10 and Linux.
The question of multi GPU support in Vulkan first popped up at GDC earlier this month. Since then, it has been reported that SLI/Crossfire functionality would be tied to Windows 10 but that is not the case. In an updated developer blog, Khronos clarified the situation: “The good news is that the Vulkan multi-GPU specification is very definitely NOT tied to Windows 10. It is possible to implement the Vulkan multi-GPU extension on any desktop OS including Windows 7, 8.X and 10 and Linux.”
There was cause for confusion though. At GDC this year. some Khronos presentations mentioned that Vulkan multi GPU functionality required the Windows Display Driver Model to be in Linked Display Adapter mode. This led to the assumption that multi-GPU setups wouldn’t work with Vulkan on Windows 7 or Windows 8.1 but that appears to not be the case.
The use of WDDM is required for Windows operating systems to take advantage of the Vulkan multi GPU extension. However, LDA mode is not explicitly required, it can just make the implementation easier. If a developer does decide to use LDA mode, it is not specifically tied to Windows 10 and can be used on other versions of the OS, including Windows 7 and 8. According to Khronos Group, there are already developers planning to ship games with this level of multi-GPU support included.
KitGuru Says: After talking about Star Citizen’s switch from DX12 to Vulkan, we received a ton of comments complaining about the lack of multi-GPU support on older versions of Windows. Fortunately, it looks like the situation was misconstrued this time around, so those sticking to Windows 7 or Windows 8.1 will still benefit from their SLI or Crossfire setups in Vulkan games. Well, as long as developers choose to use Vulkan’s multi GPU extension.