OS Limitations of Vulkan Multi-GPU Support

Subject: Graphics Cards | March 21, 2017 - 07:47 PM |
Tagged: windows 10, vulkan, sli, multi-gpu, crossfire

Update (March 22nd @ 3:50pm EDT): And the Khronos Group has just responded to my follow-up questions. LDA has existed since Windows Vista, at the time for assisting with SLI and Crossfire support. Its implementation has changed in Windows 10, but that's not really relevant for Vulkan's multi-GPU support. To prove this, they showed LDA referenced in a Windows 8.1 MSDN post.

In short:

Vulkan's multi-GPU extensions can be used on Windows 7 and Windows 8.x. The exact process will vary from OS to OS, but the GPU vendor can implement these extensions if they choose, and LDA mode isn't exclusive to Windows 10.


Update (March 21st @ 11:55pm EDT): I came across a Microsoft Support page that discusses issues with LDA in Windows 7, so it seems like that functionality isn't limited to WDDM 2.0 and Windows 10. (Why have a support page otherwise?) Previously, I looked up an MSDN article that had it listed as a WDDM 2.0 feature, so I figured DSOGaming's assertion that it was introduced with WDDM 2.0 was correct.

As such, LDA might not require a GPU vendor's implementation at all. It'll probably be more clear when the Khronos Group responds to my earlier request, though.

That said, we're arguing over how much a GPU vendor needs to implement; either way, it will be possible to use the multi-GPU extensions in Windows 7 and Windows 8.x if the driver supports it.

Update (March 21st @ 7:30pm EDT): The Khronos Group has just released their statement. It's still a bit unclear, and I've submit another request for clarification.

Specifically, the third statement:

If an implementation on Windows does decide to use LDA mode, it is NOT tied to Windows 10. LDA mode has been available on many versions of Windows, including Windows 7 and 8.X.

... doesn't elaborate what is required for LDA mode on Windows outside of 10. (It could be Microsoft-supported, vendor-supported, or something else entirely.) I'll update again when that information is available. For now, it seems like the table, below, should actually look something like this:

  Implicit Multi-GPU
(LDA Implicit)
Explicit Multi-GPU
(LDA Explicit)
Unlinked Multi-GPU
Windows 7 Requires GPU Vendor
LDA Implementation?

(Or Equivalent)
Requires GPU Vendor
LDA Implementation?

(Or Equivalent)
Windows 8.1 Requires GPU Vendor
LDA Implementation?

(Or Equivalent)
Requires GPU Vendor
LDA Implementation?

(Or Equivalent)
Windows 10
macOS Apple doesn't allow the Vulkan API to ship in graphics drivers.
At all.
Linux / etc.

... but we will update, again, should this be inaccurate.

Update (March 20th @ 3:50pm EDT): The Khronos Group has just responded that the other posts are incorrect. They haven't yet confirmed whether this post (which separates "device groups" from the more general "multi-GPU in Vulkan") is correct, though, because they're preparing an official statement. We'll update when we have more info.

Original Post Below (March 19th @ 9:36pm EDT)

A couple of days ago, some sites have noticed a bullet point that claims Windows-based GPU drivers will need WDDM in “linked display adapter” mode for “Native multi-GPU support for NVIDIA SLI and AMD Crossfire platforms” on Vulkan. This note came from an official slide deck by the Khronos Group, which was published during the recent Game Developers Conference, GDC 2017. The concern is that “linked display adapter” mode is a part of WDDM 2.0, which is exclusive to Windows 10.

This is being interpreted as “Vulkan does not support multi-GPU under Windows 7 or 8.x”.

View Full Size

I reached out to the Khronos Group for clarification, but I’m fairly sure I know what this does (and doesn’t) mean. Rather than starting with a written out explanation in prose, I will summarize it into a table, below, outlining what is possible on each platform. I will then elaborate below that.

  Implicit Multi-GPU
(LDA Implicit)
Explicit Multi-GPU
(LDA Explicit)
Unlinked Multi-GPU
Windows 7    
Windows 8.1    
Windows 10
macOS Apple doesn't allow the Vulkan API to ship in graphics drivers.
At all.
Linux / etc.

So the good news is that it’s possible for a game developer to support multi-GPU (through what DirectX 12 would call MDA) on Windows 7 and Windows 8.x; the bad news is that no-one might bother with the heavy lifting. Linked display adapters allow the developer to assume that all GPUs are roughly the same performance, have the same amount of usable memory, and can be accessed through a single driver interface. On top of these assumptions, device groups also hide some annoying and tedious work inside the graphics driver, like producing a texture on one graphics card and quickly giving it to another GPU for rendering.

Basically, if the developer will go through the trouble of supporting AMD + NVIDIA or discrete GPU + integrated GPU systems, then they can support Windows 7 / 8.x in multi-GPU as well. Otherwise? Your extra GPUs will be sitting out unless you switch to DirectX 11 or OpenGL (or you use it for video encoding or something else outside the game).

On the other hand, this limitation might pressure some developers to support unlinked multi-GPU configurations. There are some interesting possibilities, including post-processing, GPGPU tasks like AI visibility and physics, and so forth, which might be ignored in titles whose developers were seduced by the simplicity of device groups. On the whole, device groups was apparently a high-priority request by game developers, and its inclusion will lead to more multi-GPU content. Developers who can justify doing it themselves, though, now have another reason to bother re-inventing a few wheels.

Or... you could just use Linux. That works, too.

Again, we are still waiting on the Khronos Group to confirm this story. See the latest update, above.

Video News

March 19, 2017 | 09:52 PM - Posted by willmore

So, once my windows 7 box dies, it's back to Linux for all of my machines. Can't say as I'll miss that flakey OS.

Fortunately, Linux support everything without any silly limitations.

You wanted people off of Win7, Microsoft. Guess you'll get it.

March 19, 2017 | 10:21 PM - Posted by remc86007

"Linux support[sic] everything without any silly limitations."

I know what you mean, but, although it may not have any limitations preventing applications from running on it, the problem is that the vast majority of programs that powerusers and gamers use are either not compatible or run worse on Linux.

Linux has its uses, but being a primary desktop OS isn't one of them.

March 19, 2017 | 10:55 PM - Posted by Anonymous (not verified)

You can keep saying that, but there will be many that will take any Linux gaming performance they can get as the MOST logical option to ever choosing windows 10's closed spyware/adware/cloudware bloat driven OS ecosystem!

Some People want control over their OS and the privacy that is offered by Linux, and you will be shocked at what can and will happen over the next 3 years that Windows 7 has remaining and before some larger number people will be forced over to using Linux!

The Ryzen 7 SKUs offer plenty of cores in which to run windows 7(After 2020) in a locked down Linux Kernel based VM instance and game that way, all while having plenty of more time for the Linux gaming ecosystem to get better. Valve is still supporting Steam OS development, as Valve's very existence depends on having Linux gaming support!

Linux only needs about 5-10% market coverage for gaming Desktop/Laptop support before things will start to reach a tipping point! And with most non technical consumers going with their phones and Linux/Vulkan support there also, Vulkan the API already has a larger devices market install base than any PC/Laptop only market. So don’t kid yourself into thinking that Vulkan lacks any real and very large importance as a development target!

Tim and Gaben are 100% correct in that alternative need for Linux Gaming and the games makers are also with each and every M$ move starting to see how things really are planed out for the windows 10 closed ecosystem! And those folks do not like what they see and have not liked it since windows 8 and TIFKAM(Now named UWP and still not liked).

March 22, 2017 | 11:46 AM - Posted by Anonymous (not verified)

Keep dreaming

March 22, 2017 | 08:38 PM - Posted by Anonymous (not verified)

Vulkan/Linux for a spyware free OS experience, without M$ all up in your business!

March 20, 2017 | 08:41 AM - Posted by Anonymous (not verified)

Although closed source software is not inherently bad, the problem is that, with closed source software, the developer is ultimately in control of a product even after it has 'sold' it to a customer and will take advantage of the user in every way it can expect to get away with. And with a product as complex to migrate from as an OS, they can expect to get away with a lot.
I'm not worried about not being in control of non-essential software like games, but my primary desktop OS is just too important.

April 22, 2019 | 08:43 PM - Posted by Sjoer van der Ploeg (not verified)

There is no such thing as a Power User using Windows as his main OS, firstly he does not care and secondly he probably has more Linux devices.

March 20, 2017 | 08:11 AM - Posted by kal (not verified)

Linux may support everything, but I have yet to see anything or anyone support Linux on a serious level in regards to gaming.

Valve stepped forward then backed off into a shadow. Assuming game developers and the 800 dozen custom PC builders would just ship SteamOS on their systems without any support from a software, input or driver standpoint directly from Valve. The end result being games ran half as good - performance wise, compared to Windows with no word from Valve as to what is actually happening with SteamOS in the mainstream gaming space.

Linux can't be taken seriously for anything despite its benefits because those who speak of it aren't fully devoted. Everybody acts as though they hate Windows for gaming while at the very same time don't have the balls to jump ship, in the hopes that developers will take notice & turn to linux as the primary OS.

Linux sounds great in theory, until you install the damn thing, sudo pack BS a hundred different drivers, then you realize there's nothing on there worth doing unless you're in to programming. Windows is dominant for a reason. Devs will improve on it where ever possible and like the rest, everyone will soon be on Windows 10. 7 is dead, and Linux holds about as much relevancy as Microsoft Zune.

March 20, 2017 | 12:02 PM - Posted by Anonymous (not verified)

Valve's current library show over 6.5k games that support Linux versus 28k Windows titles, that's not what I'd call backing off into the shadows.

People don't hate Windows for gaming, quite the contrary as many people use it just for gaming, people hate Windows for many reasons however like you say it's the best gaming OS for the PC on the market and there's little chance of that changing all the while the majority of people keep using it.

March 22, 2017 | 11:47 AM - Posted by Anonymous (not verified)

Exactly this

March 22, 2017 | 08:47 PM - Posted by Anonymous (not verified)

7 is the new XP and running Vulkan safely locked down inside a Linux Kernel based Virtual Machine instance on an 8 core Ryzen SKU for some gaming/other uses after 2020. Linux gaming is progressing and any games that need 7 after 2020 can run inside that Virtual Machine instance.

Enterprises are still running XP safely inside a Linux Kernel based Virtual Machine instance for any applications that need XP. Ditto for windows 7 after 2020, and all those Ryzen affordable 8 core SKUs will mean that some home users will have that ability with all the available Ryzen cores.

If windows 7 with the most windows users is dead then widows 10 with its smaller market share after this amount of time is dead, dried up and blown away!

April 22, 2019 | 08:32 PM - Posted by Sjoer van der Ploeg (not verified)

Linux is used more than you realize, this forum is most likely also hosted on a Linux server.

The whole damn internet is probably served to you through multiple devices running Linux.

Besides all of that, you can run most games through DXVK and get near native performance.

You all speak of Linux as if there is "nothing" to-do? What else do you actually do that requires Windows? Probably nothing.

March 19, 2017 | 10:00 PM - Posted by Anonymous (not verified)

Vulkan it is for Star Citizen's crowdfunded project!

"Star Citizen Plans To Go Vulkan-Only"


March 20, 2017 | 10:53 AM - Posted by Anonymous (not verified)

You do know their announcement about Vulkan only is just so they can delay a release even more, right?

March 20, 2017 | 11:50 AM - Posted by Anonymous (not verified)

It does not matter to me, as long as I can get a Linux OS OEM made laptop without M$, Intel, and Nvidia inside, I'll be very happy to give any Linux/Vulkan project my support.

I'm really looking forward to having a Zen/Vega APU coming in in a Linux OS OEM made laptop offering for my laptop needs! The PC folks are already having those Linux Options, but OEM laptops that support a Full Linux OS build out of the box and do not include Intel/Nvidia inside are very rare currently!

I can hold out until 2020/2023 at the latest, but with 3 more years before 7 goes EOL there should be at least one Linux OEM laptop without any M$, Intel, and Nvidia dependencies!

March 23, 2017 | 02:29 AM - Posted by Anonymous (not verified)

May I ask what is wrong with Intel?

March 23, 2017 | 10:59 AM - Posted by Anonymous (not verified)

Abusive monopoly Intel(1), had to pay AMD 1.25 billion(2) dollar fine for illegal market practices! Intel paid OEMs to not use AMD's products!


"A.M.D. Suit Says Intel Bullied Clients"



"Intel’s $1.25 Billion Settlement"


March 20, 2017 | 12:08 PM - Posted by Anonymous (not verified)

How is changing your plan that instead of eventually moving to DX12 you're going to use Vulkan going to delay things?

Neither of them have been implemented yet so all they've done is change what the intended to do in the future.

March 21, 2017 | 07:58 AM - Posted by Anonymous (not verified)

It means they can justify yet another delay instead of finishing the game.
You know... "The work we did towards DX12 has to be scrapped and we have to start over again".
I'm just waiting for the day when people start looking at the project without rose tinted glasses on.

March 21, 2017 | 11:50 AM - Posted by Anonymous (not verified)

What you mean the work they've not even started yet?

Chris Roberts said on September 2015 that the refactoring of the low-end of the engine to support more draw calls would take a year, and that what would work [for Dx12] will [also] work for Vulkan.

The fact is the change from DX12 to Vulkan involves minimal developer time, I'd be amazed if it took up more than a few days.

March 21, 2017 | 09:49 PM - Posted by John H (not verified)

They should just finish on dx11 and get squadron 42 out. Dec 2014 was the original promise date.

Also vulkan may require more work than dx12. It's not automatically apples to apples.

March 22, 2017 | 11:48 AM - Posted by Anonymous (not verified)

That's even more sad.

March 22, 2017 | 08:48 PM - Posted by Anonymous (not verified)

UWP, now that's some Vaporware!

March 19, 2017 | 10:26 PM - Posted by odizzido (not verified)

Can all of the game devs please just stop using directx?

March 19, 2017 | 10:46 PM - Posted by gamerk2 (not verified)

Here's my issue: On Windows, you can only have one display driver installed. So you have no visibility into devices from other manufactures. So there's no way this will be supported.

March 19, 2017 | 11:11 PM - Posted by Scott Michaud

Windows XP, 7, 8, and 10 all support multiple graphics drivers. The only one that didn't was Windows Vista.

March 19, 2017 | 11:18 PM - Posted by Anonymous (not verified)

It's best to have the Vulkan API managed multi-GPU and use the simplest drivers and let the Gaming Engine makers all pool their resources to develop in their Gaming Engine SDKs/Middle-ware an easy way to manage milti-GPU in games.

There are plenty of software engineers in and among the Gaming/Gaming engine industry and colleges and universities to make any middle-ware to automate the production of software for any non systems software engineer level programmers to take advantage of Vulkan API managed multi-GPU adaptor usage.

AMD has the ROCm open-source middle-ware to assist for GPU usage in gaming and GPU compute acceleration/Professional settings. So Linux/Vulkan and more industry/academic work to manage any GPUs plugged into a PC/laptop/other computing platform!

All this vendor lock-in Hardware/OS/API(Non Open API) nonsense is just holding back progress to protect some big interests’ revenue streams!

March 19, 2017 | 11:51 PM - Posted by Anonymous (not verified)

The claim that OS X will not support Vulkan is wrong; Apple is creating a wrapper for Vulkan on top of Metal.

Vulkan doesn't "ship graphics drivers" themselves because they don't need to.

March 20, 2017 | 12:19 AM - Posted by Scott Michaud
  1. MoltenVK isn't made by Apple, and it's a wrapper around Metal (as you said).
  2. Even if it was made by Apple, native implementations are still banned from drivers.
  3. I said ship in graphics drivers.
March 20, 2017 | 12:54 AM - Posted by Anonymous (not verified)

I'm absolutely for graphics drivers that only do one thing! And that is to only minimally abstract at the lowest possible level the GPU's actual metal/silicon/whatever element is used to make the GPU.

Graphics drivers should only be allowed to abstract the hardware at the minimal lowest level with any other functionality under the control of the Graphics API/OS and the software and Gaming engine/Gaming middle-ware level via calls to the Graphics API/OS.

The GPU’s makers should have been told to make their GPU drivers minimal and close to the metal or face not getting their hardware white-listed for use under any of the OS/graphics API makers support, Linux, MacOS, or otherwise.

Any multi-GPU/other processing load balancing belongs properly under the control of OS/Graphics API and software, and games software/Gaming engines that can call on the OS/Graphics APIs or other OS managed APIs to get at the simplified drivers that get at the CPU’s/GPU’s “Metal”.

An eternal ripoff it has been that the GPU makers should have ever been allowed to have any multi-GPU processor control that should have been in the domain of the OS/Graphics APIs and the larger sphere of processor programming knowledge represented by the OS and Graphics API related disciples. This CF/SLI nonsense has been a kludge from day one and has resulted in so much unacceptable slowing of the proper levels of progress in the entire history of computing!

March 20, 2017 | 06:05 PM - Posted by Anonymous (not verified)

4. MoltenVK isn't actually very useful anyway, unless completely absent support for compute/geometry/tessellation shaders is acceptable for your use-case.

March 20, 2017 | 01:34 AM - Posted by Anonymous (not verified)

I think Microsoft wants to create a walled garden in the gaming market. Closing off the PC market to competitors will be difficult, but I think they will still make it more difficult for developers to release on PC without going through the windows store somehow so Microsoft can take a cut. I suspect their main method of moving gamers into a closed ecosystem will be through releasing a higher performance console. If they can get people to buy a more expensive, more powerful console instead of a PC, they they don't have to close off the PC ecosystem. They just have to get people to willingly move into their walled garden. If Scorpio can pull off a kind of mid-range gaming experience, then I could see people moving to it rather than deal with the complexity and expense of a gaming PC. Also, they could release a VR and/or AR headset, but only as an Xbox accessory. I don't game much and I use linux at home (partially for work), so I would prefer that there be more games for Linux. Linux still has its issues though. I never did get the current version of lubuntu I am using to print properly. Also the sound didn't work without manual tinkering. I actually haven't used windows at home since Windows 98 though, so I don't think I am going to start using it now.

Posted from my iPhone.

March 20, 2017 | 04:54 AM - Posted by Anonymous (not verified)

"I think Microsoft wants to create a walled garden in the gaming market [...] Posted from my iPhone. "


Joking aside, claims that "Microsoft want to make Windows a walled garden!" have been made repeatedly for over a decade now, and it's yet to happen. The main reason is that Microsoft is funded not by consumer OS sales, but enterprise OS licensing. And Microsoft keeps selling enterprise OS licenses because Windows runs existing Win32 API programs, while OSX and Linux do not. If they were to stop supporting Win32 they would basically be cutting off their main source of revenue, and removing Win32 would be a prerequisite for setting up any sort of 'walled garden' style distribution model.

As Intel found with Itanium, and AMD found with HSA, trying to persuade every software developer on the planet to re-write their program (even just a little) to support your new API or architecture is Not Going To Happen. x86 will abide, and Win32 will abide.

March 20, 2017 | 11:38 AM - Posted by Anonymous (not verified)

And M$'s progress in doing its walled garden has been slowed by Valve's Gaben/Linux community developing a Linux OS gaming ecosystem. Make no mistake about it Gaben came and looked at MS's Terrible TIFKAM(Now called UWP) windows 8 and was forced create that Steam OS ecosystem or else face extinction. M$ is now and was forced to slow its nefarious plans to a crawl but M$ is gradually and insidiously making its move to that very closed ecosystem all while hiring plenty of paid apologists to spin out their tales of plausible deniability!

M$ has already factored in the cost of loosing some market share into its costs of going full on beyond even an Apple style closed ecosystem on folks’ third party OEM made PC/Laptop hardware and also their home built PCs! M$ is a cloud and services company by explicit statement and windows 10 will become that cloud and services portal with 30% off of the top of any action(Gaming/wherever), plus the personal metrics gathering and the ads pushed out from the OS revenue streams.

The hour hand is still slow, imperceptibly slow, but it still makes its progress, and M$ can bide its time. People keep a keen eye on that UEFI/BIOS that comes on any OEM PC/Laptop that comes with windows 10 factory installed. M$ will try and try again if people do not practice constant vigilance with respect to M$ and M$’s real intentions!

March 20, 2017 | 04:54 AM - Posted by Anonymous (not verified)

What about game consoles and android?

March 20, 2017 | 08:47 AM - Posted by Anonymous (not verified)

Umm what about it? Wrong topic maybe?

March 20, 2017 | 09:06 AM - Posted by Anonymous (not verified)

Playing stupid?

March 20, 2017 | 03:14 PM - Posted by Anonymous (not verified)

Android doesn't support LDA or MDA or anything really. MDA support could work in theory but since there's no Android devices with multiple parallel compute units and no SLI drivers for Android umm... I don't know what you're asking.

March 21, 2017 | 06:40 PM - Posted by Scott Michaud

Other platforms with multiple GPUs fall under "etc." or no Vulkan support as far as I know.

March 20, 2017 | 06:45 AM - Posted by drbaltazar (not verified)

Hey paper! You are a dev tomorrow morning (humor me)you got the simplicity of console .would you bother with all the various ways thing can go wrong on PC ? It's like wanting to raid end level content at level 1 in world of Warcraft lol.
Most dev will code like on console .job done .

March 20, 2017 | 11:58 AM - Posted by Anonymous (not verified)

Apple's Metal API is related to Vulkan. So Apple does allow a form of Vulkan to run on it's hardware.

March 20, 2017 | 12:34 PM - Posted by Anonymous (not verified)

Yes, but as the author states correctly....Vulkan is not allowed to be nativly implemented in drivers.

March 20, 2017 | 12:50 PM - Posted by Gunbuster

Seems like a lot of work for devs to allow a user to add in a hooptie old graphics card to the mix and get probably 20%+ performance at best.

March 20, 2017 | 06:02 PM - Posted by Scott Michaud

That depends on your metric of performance. If you can quadruple your physics or AI actors with zero slowdown, then you didn't have "+0% performance", even though your frame rate didn't budge.

March 20, 2017 | 01:01 PM - Posted by Anonymous (not verified)

The real need is all of it is supported under Linux. The sooner I can dump my remaining windows gaming rig, the better.

March 20, 2017 | 03:01 PM - Posted by Anonymous (not verified)

We need Greenpeace to force use of Vulkan.

March 20, 2017 | 03:23 PM - Posted by Anonymous (not verified)

Why! M$'s forcing of the updates that force all that spyware, adware, bloatware is doing that much more for Vulkan/Linux adoption without any Greenpeace involvment necessary! M$'s actions under windows 10 will be what makes it so very attractive to toss all that DX12 nonsense and any neeed for windows 10 and go all in with Vulkan/Linux.

Vulkan will be what most will use phone to supercomputer running atop the Linux Kernel.

March 21, 2017 | 02:42 PM - Posted by ThE_MarD

Heyyo, Thank you very much, Scott Michaud for making this article. It has been driving me crazy that everyone is reporting this wrong. Vulkan MDA has been supported since last year and now everyone thinks Vulkan Multi-GPU is Windows 10 only... albeit, I sadly doubt MDA will get much widespread use, even once popular game engines support it since LDA is the "safer bet" to use and support...

March 21, 2017 | 03:25 PM - Posted by Scott Michaud

Yeah... as far as I know, the only way to ban MDA (with the way Vulkan is set up) is to incorrectly enumerate graphics devices. I seriously doubt that would happen.

Btw... the Khronos Group is (apparently) still preparing an official statement on the matter. The story could change significantly any second now.

March 21, 2017 | 03:31 PM - Posted by Anonymous (not verified)

As the headline below reads: Can there be any ore reason to dump both M$ and Adobe! Linux/Vulkan and my hardware is actually mine!

"Adobe buddies up with Microsoft for new ways to mine your data

Announces product integrations and new language for exchanging customer data"


March 21, 2017 | 09:42 PM - Posted by gamerk2 (not verified)

Stupid question: WDDM limits the number of display adapters to one. How the heck are devs supposed to implement cross-vendor GPU support when they don't have the benefit of display drivers for both NVIDIA & AMD? Or do you suggest we go back to the days where GPU support is manually hardcoded into games to support specific GPUs/combinations?

Sorry, but cross-vendor GPU support isn't happening for that very simple reason.

March 22, 2017 | 12:01 AM - Posted by Scott Michaud

That's not how it works. You just manage multiple command lists that point to different GPUs. This was possible on Windows XP, 7, 8.x, and 10 (but not Vista). All you need to do is enumerate all possible devices. In fact, I've done this, personally, in OpenCL.

This isn't to say it's easy... it's not. You need to make sure that the performance is roughly balanced and the output is consistent enough to be a good user experience. But no, it's not something like "manually hard code specific GPU combinations into the game". Oxide Games, for instance, just gave users a selection menu, although that might not fly outside of the enthusiast space.

March 21, 2017 | 09:42 PM - Posted by gamerk2 (not verified)

Stupid question: WDDM limits the number of display adapters to one. How the heck are devs supposed to implement cross-vendor GPU support when they don't have the benefit of display drivers for both NVIDIA & AMD? Or do you suggest we go back to the days where GPU support is manually hardcoded into games to support specific GPUs/combinations?

Sorry, but cross-vendor GPU support isn't happening for that very simple reason.

March 21, 2017 | 10:44 PM - Posted by Anonymous (not verified)

Games can use the Vulkan aware simplified graphics drivers/graphics driver functionality provided by the GPUs makers' that is not tied into that Windows WDDM functionality and use the Vulkan Multi-GPU(Unlinked method). So when you install the GPU’s drivers, the Vulkan graphics drivers for that GPU, the GPU makers can supply Vulkan Drivers for whatever version of windows/Linux/Other OS for their GPU hardware.

Vulkan's Multi-GPU(Unlinked) method is the cross platform way to implement any multi-GPU/Vulkan games/software. That "LDA" stuff is all tied into WDDM and that's not cross platform anyways! I’ll bet that the Vulkan generic unlinked method will do fine for any cross vendor Multi-GPU usage since they do not have to make use of any WDDM functionality.

It's best to maybe go full on Linux for gaming as there is no WDDM/proprietary types of restrictions in Linux. There is no telling what M$ may do to throw a Ballmer monkey wrench into the works under windows.

March 21, 2017 | 10:07 PM - Posted by Anonymous (not verified)

From Phoronix(1). So it looks like Vulkan's NON WDDM dependent method is the way to go for all OSs windows or Linux/others and forget about WDDM and only use the Vulkan multi-GPU(Unlinked). I'd want to steer clear of any M$ specific usage models for Multi-GPU/Vulkan and so that generic Vulkan multi-GPU(Unlinked) way is good. I do not trust M$'s WDDM or any future WDDM shenanigans in windows 7, 8.x, or windows 10(I'll never use 10).

"The Khronos Group has now issued a state that WDDM is only needed for Vulkan multi-GPU on Windows 10 while WDDM isn't otherwise necessary. Even on Windows, if Vulkan drivers choose not to use WDDM's Linked Display Adapter (LDA) mode, the Vulkan multi-GPU support can run on Windows 10 and older versions of Windows. There's nothing stopping Linux drivers -- or Vulkan drivers from other operating systems -- from implementing Vulkan multi-GPU either." (1)


"Khronos Clarifies That Vulkan Multi-GPU Isn't Limited To Windows 10"


March 22, 2017 | 04:59 PM - Posted by Captain Calamity (not verified)

Well thanks for creating a panic out of a non-story

March 22, 2017 | 05:01 PM - Posted by Captain Calamity (not verified)

I mean really, what was the rush in getting the story out, especially when you did not have accurate information?

is getting the scoop really more important then journalistic integrity?

March 23, 2017 | 10:21 PM - Posted by Scott Michaud

The ethical thing to do is often to publish, with what you know, what you don't know, and what you're waiting to confirm properly labeled, as you know it. That is journalistic integrity.

In this case, the initial post was to state that the Khronos Group's slide did not apply to MDA mode (when other sites didn't make the distinction). That is important information for people know.

It sometimes makes sense to hold back a little, but that's a judgement call to be made on an individual basis. For instance, what if I never got a response? Does it make sense to bury every story that a company doesn't want to talk about?

That said, you can disagree with my decision to publish on Sunday evening (when I emailed the Khronos Group on Saturday) versus, let's say giving them Monday for a work day... and that's fine. That's a valid complaint, especially since I had almost every reason to believe that the Khronos Group was going to respond during the work week.

As for "did not have accurate information": it was an official slide from the Khronos Group, cross-referenced with MSDN posts and my knowledge of Windows 10 / DirectX 12. As it turns out, the slide overplayed the importance of LDA to the extension, and the MSDN posts that I found, which list LDA as a WDDM 2.0 feature, ignore the prior implementation (designed for Vista-era SLI and Crossfire) that could be used for Vulkan drivers.

Really, the most ironic part of this situation is that I knew, if I drew attention to the fact that I was waiting for confirmation, it would make people more likely to accuse me of clickbaiting. (It gets people thinking about it.) It's the same as when I mention known issues in graphics drivers posts, which make people accuse me of overlooking issues (or overplaying issues) for specific companies. However, it's the right thing to do, so I do it.

March 22, 2017 | 05:38 PM - Posted by Anonymous (not verified)

These things has been known almost a year now. Don't know what is the fuss about now.

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