Sometimes the Internet gets things wrong (shocking revelation, right?). That was the case earlier this week when it was widely reported that Khronos Group's Vulkan API would not support multiple GPU setups on versions of Windows prior to Windows 10. As it turns out, it will.
In no uncertain terms, Khronos Group said confirmed that "the multi-GPU specification is very definitely NOT tied to Windows 10, and that "it is possible to implement the Vulkan multi-GPU extension on any desktop OS, including Windows 7, 8.x, and 10 and Linux."
This is in stark contrast to Microsoft's competing low-level DirectX 12 API, which very definitely IS tied to Windows 10. So why the confusion over Vulkan? In short, it stemmed over a misunderstanding of slides presented at GDC.
The folks at Dark Side of Gaming pointed out that in one of Khronos Group's slides, it said that in order to natively support SLI and Crossfire setups "WDDM must be in 'linked display adapter' (LDA) mode." WDDM 2.0 is exclusive to Windows 10, so the assumption was that Vulkan's multi-GPU functions "will most probably not work under Windows 7 or Windows 8.1."
Khronos Group admitted that its slide wasn't real clear on the matter and acknowledged that it led to some confusion. To set the record straight, Khronos Group provided an update saying WDDM (Windows Display Driver Model) isn't needed to implement the Vulkan multi-GPU extension on non-Windows OSes, such as Linux.
The group also clarified that on Windows, the use of LDA mode to implement Vulkan multi-GPU functionality "is not strictly necessary," though it does make things considerably easier and will probably be the preferred option for most developers. And to reiterate, when developers do use LDA mode, they're not tied to Windows 10.
"LDA mode has been available on many versions of Windows, including Windows 7 and 8.x," Khronos Group said.
This is obviously good news for proponents of Vulkan who are rocking multiple GPU setups on older versions of Windows. It also might motivate developers to choose Vulkan over DX12. It's worth mentioning that Star Citizen is dropping DirectX support in favor of Vulkan. Cloud Imperium Games developer Ali Brown said the decision was made because Vulkan enables single-API support for older versions of Windows (and Linux) without sacrificing performance and features.
"Years ago we stated our intention to support DX12, but since the introduction of Vulkan which has the same feature set and performance advantages this seemed a much more logical rendering API to use as it doesn't force our users to upgrade to Windows 10 and opens the door for a single graphics API that could be used on all Windows 7, 8, 10, and Linux," Brown said.
Let the API wars begin in earnest.
