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
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  • Scootiep7 - Thursday, October 29, 2015 - link

    Actually, shouldn't that be switched? Brown would be the additive tertiary color wheel result, and yellow would be the subtractive tertiary color wheel result last I checked. Reply
  • xenol - Monday, October 26, 2015 - link

    Now we can finally put this AMD vs. NVIDIA war to rest. Get both cards to get exclusive technologies, then when the game supports it, get the best horsepower of both. Reply
  • Tunnah - Monday, October 26, 2015 - link

    We need to see the SLI/Xfire numbers first. It's all kinda pointless if 2 980Tis trounce em all Reply
  • silverblue - Monday, October 26, 2015 - link

    I doubt two 980 TIs would make much of a difference over a 980 TI and a Titan X. Reply
  • Refuge - Monday, October 26, 2015 - link

    i think you are crazy if you are going to use any of these numbers for any argument, or buying decision.

    While interesting information to digest, it is merely that, this isn't Beta, this isn't even Alpha, this is is literally engineers saying "Hey guys check this shit out!"

    I love what I'm seeing so far though, this is exciting, but the thought of EA, Bethesda, and Ubisoft being in control of so much does scare me...

    EA = Pure evil

    Bethesda = Tree's sticking through walls, Dragons having seizures in the air, and Chickens reporting your crimes to the local Police.

    And Ubisoft? Well... I haven't given them much credit since the mid to late 90's...
    Reply
  • naretla - Tuesday, October 27, 2015 - link

    EA hasn't been the worst publisher for some time now. You could call them greedy, but at least they're relatively competent. Reply
  • Refuge - Tuesday, October 27, 2015 - link

    Sim city, and Dragon Age Inquisition beg to differ. Reply
  • naretla - Tuesday, October 27, 2015 - link

    Yeah, they went too far with SimCity, but it's been over two and a half years since then. Please elaborate re:DAI. Reply
  • Refuge - Tuesday, October 27, 2015 - link

    I pre-ordered that game, against my better judgment I admit, and I wasn't able to play it for months because of fucking bugs. I won't pre-order anything from anyone until I see a change in the way these companies do business.

    I also agree that Simcity was a long time ago, but I've also not forgotten. I won't expect them to do better until I see them doing better.

    it isn't just EA though, I won't pre-order Fallout 4 either for the very same reasons. Different publisher/Developer, but still the industry has left me jaded.

    It is insulting to me when a publisher thinks that I'm stupid enough to be ok with paying full price for a game, only to get a beta build.

    Its antics like that, that give me pause for celebration over all the new fine grained controls offered by DX12.

    The potential is huge, the power and life extracted from the X 360, and PS3 were impressive towards the end of their life cycle, and I would love to see what they could do back then had they had the control they are being offered now. I also agree that the Dev's are the best ones to make the most of this technology.

    But Dev's (unless Indie) are under the thumb of Publishers like EA, and their deadlines and budgets. It is this that gives me a lot of fear about the half baked disasters that could this way be headed.
    Reply
  • SunnyNW - Tuesday, October 27, 2015 - link

    I would think that the GPU vendors would help game developers with engineering resources. Probably not with this particular setup (EMA) but with say like Split Frame Rendering with two identical GPUs being utilized. Reply

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