Throughout this year we’ve looked at several previews and technical demos of DirectX 12 technologies, both before and after the launch of Windows 10 in July. As the most significant update to the DirectX API since DirectX 10 in 2007, the release of DirectX 12 marks the beginning of a major overhaul of how developers will program for modern GPUs. So to say there’s quite a bit of interest in it – both from consumers and developers – would be an understatement.

In putting together the DirectX 12 specification, Microsoft and their partners planned for the long haul, present and future. DirectX 12 has a number of immediately useful features in it that has developers grinning from ear to ear, but at the same time given the fact that another transition like this will not happen for many years (if at all), DirectX 12 and the update to the underlying display driver foundation were meant to be very forward looking and to pack in as many advanced features as would be reasonable. Consequently the first retail games such as this quarter’s Fable Legends will just scratch the surface of what the API can do, as developers are still in the process of understanding the API and writing new engines around it, and GPU driver developers are similarly still hammering out their code and improving their DirectX 12 functionality.

Of everything that has been written about DirectX 12 so far, the bulk of the focus has been on the immediate benefits of the low-level nature of the API, and this is for a good reason. The greatly reduced driver overhead and better ability to spread out work submission over multiple CPU cores stands to be extremely useful for game developers, especially as the CPU submission bottleneck is among the greatest bottlenecks facing GPUs today. Even then, taking full advantage of this functionality will take some time as developers have become accustomed to minimizing the use of draw calls to work around the bottleneck, so it is safe to say that we are at the start of what is going to be a long transition for gamers and game developers.

A little farther out on the horizon than the driver overhead improvements are DirectX 12’s improvements to multi-GPU functionality. Traditionally the domain of drivers – developers have little control under DirectX 11 – DirectX 12’s explicit controls extend to multi-GPU rendering as well. It is now up to developers to decide if they want to use multiple GPUs and how they want to use them. And with explicit control over the GPUs along with the deep understanding that only a game’s developer can have for the layout of their rendering pipeline, DirectX 12 gives developers the freedom to do things that could never be done before.

That brings us to today’s article, an initial look into the multi-GPU capabilities of DirectX 12. Developer Oxide Games, who is responsible for the popular Star Swarm demo we looked at earlier this year, has taken the underlying Nitrous engine and are ramping up for the 2016 release of the first retail game using the engine, Ashes of the Singularity. As part of their ongoing efforts to Nitrous as a testbed for DirectX 12 technologies and in conjunction with last week’s Steam Early Access release of the game, Oxide has sent over a very special build of Ashes.

What makes this build so special is that it’s the first game demo for DirectX 12’s multi-GPU Explicit Multi-Adapter (AKA Multi Display Adapter) functionality. We’ll go into a bit more on Explicit Multi-Adapter in a bit, but in short it is one of DirectX 12’s two multi-GPU modes, and thanks to the explicit controls offered by the API, allows for disparate GPUs to be paired up. More than SLI and more than Crossfire, EMA allows for dissimilar GPUs to be used in conjunction with each other, and productively at that.

So in an article only fitting for the week of Halloween, today we will be combining NVIDIA GeForce and AMD Radeon cards into a single system – a single rendering setup – to see how well Oxide’s early implementation of the technology works. It may be unnatural and perhaps even a bit unholy, but there’s something undeniably awesome about watching a single game rendered by two dissimilar cards in this fashion.

A Brief History & DirectX 12
POST A COMMENT

180 Comments

View All Comments

  • LemmingOverlord - Wednesday, October 28, 2015 - link

    Now that's what I call ... DRIFT COMPATIBLE!!!!! <cue guitar riff> Reply
  • albert89 - Wednesday, October 28, 2015 - link

    Would love to see DX12 multi-adapter work with a gaming card and a workstation card combination. Is it even possible ? Reply
  • wiak - Thursday, October 29, 2015 - link

    the reason that amd primary + mvidia is better is pretty much the GCN architecture, GCN has ACE that helps to distribute the work to the secondary nvidia gpu Reply
  • zodiacfml - Friday, October 30, 2015 - link

    Not holding my breath on this one. I would be happy though if they can put the integrated GPU to good use. Reply
  • drep - Friday, October 30, 2015 - link

    Maybe I missed it somewhere, but does this mean you no longer need the SLI link on your Nvidia cards when using dx12 with these features? I assume you dont can't you cant use a link on the AMD card. Is there a performance difference if you 2 nvidia cards using the SLI link versus if you don't use it in this bench? Reply
  • Oxford Guy - Friday, October 30, 2015 - link

    Isn't it the 290X/390X that gets the biggest performance boost from Ashes? It would be nice to have one of those included. Reply
  • gothxx - Saturday, October 31, 2015 - link

    @Ryan Smith, what does mixed GPUs mean for G-Sync/Freesync? is it possible to support both just switching which is the primary GPU and in which card the monitor is connected? Reply
  • echtogammut - Monday, November 02, 2015 - link

    You can be certain that either AMD or NVidia will kill off this ability with some driver "update". Reply
  • Haravikk - Tuesday, November 03, 2015 - link

    Promising stuff.

    I'm curious actually, but how well (if at all) does DirectX 12/Mantle interact with HSA? Presumably DirectX 12 and Mantle have their own mechanisms for handling memory use, but does either graphics API leverage HSA in systems that have it, or is that still something that developers need to do themselves? I could see that making a difference an APU iGPU + dGPU setup, maybe even more-so if the discrete graphics are also from AMD?
    Reply
  • RavenSe - Tuesday, November 03, 2015 - link

    Well actually I believe that's one of the best moves for the crowds by MS. Fck branding let them fight together and we gonna take advantage of both anyways.
    I can see Ryan said he doesn't have a clue how come mixing gets better than keeping one side. Did you look at minimums? I got a simple hunch... how about there is parts of both GPU's that handle specific task worse but since those GPU are so architecturally different, they help each other to handle those bottlenecks. I'm not sure it can work this way but that would be logical... give some task to be done for the card that can handle it better for example PhysX to nVidia and some heavy computing to AMD. This way or another thats actually the first time in my life when I'll start considering having both vendors at once in the same rig!
    Reply

Log in

Don't have an account? Sign up now