AMD revealed that it no longer refers to multi-GPU support by the long-known Radeon brand as CrossFire. This revelation comes via PCWorld's Brad Chacos, who is curious why Crossfire is not mentioned in the latest Radeon Software 17.9.2 company driver. He proceeded to send an email to AMD to inquire about this obvious omission.
Surprisingly, AMD's answer is that it switched from the CrossFire brand, calling it a DirectX 11 era technology. "CrossFire is not mentioned because it technically refers to the DX11 app," an AMD PR told PCWorld. "In DirectX 12, we are referencing multi-GPUs because the app should support mGPU, while AMD should create profiles for DX11.We have adjusted to using CrossFire tags for multi-GPU games."
AMD further elaborates by saying that this is merely a branding decision rather than a technical strategy. The company did not stop the multi-GPU support for its graphics card, in fact its newest driver enables multi-GPU support for Radeon RX Vega's newly released graphics card with the promise of 80% + performance scaling.
Multi GPU In The New DirectX 12 Era
Gone are the days of old when graphics card vendors had to craft and optimize CrossFire & SLI profiles for multi-GPUs to work altogether in the game. DirectX 12, unlike all of its predecessors, delegates this responsibility entirely to game developers through a feature called Explicit Multi-Adapter. The API allows low-level access to hardware, allowing developers to access each GPU directly and independently.
There are two types of explicit Multi-Adapter modes in DirectX12 "Linked" and "Unlinked". Linked mode is only available when there are multiple identical GPUs in the system, similar to current CrossFire and SLI configurations. This allows for computational / graphical resources and memory pools of multiple GPUs combined into one larger addressable unit. This mode works by delegating the same workload to each GPU, which basically reduces the overall work to two in order to complete it in less time.
One GPU can create one part of the frame while the second one can create another part of the same frame for example. This is called Split Frame Rendering, SFR for short. This technique negates the inherent limitations of traditional alternative frame rendering - the AFR technique - used today in DX11 and older games, which involves mirroring the memory pool and introducing the need to pacing the frame.
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Unhappy mode is a second multi-GPU option under DX12. This mode is designed to take advantage of GPUs with different capabilities and even different vendors simultaneously in the system. Yes, this allows developers to force NVIDIA and AMD GPU to work together. This mode allows this through a thin abstraction layer that allows multiple GPUs to swap data back and forth while giving total control to the developer. This mode allows developers to use discrete GPUs along with an integrated GPU or other discrete GPUs. With each GPU being treated as a truly independent graphics engine, developers can choose to take advantage of whatever they want.
It brings the concept of CrossFire and SLI, which was introduced more than a decade ago. Because you can clearly say the new multi-GPU capability of DirectX 12 has very little to do with SLI and CrossFire, which is basically a proprietary algorithm developed by each vendor to allow rendering of alternative frames through the driver's layer. Therefore calling support for DirectX 12 multi-GPU SLI or CrossFire is completely inaccurate.
DX12 in and of itself does not rely on SLI and CrossFire technologies owned by NVIDIA and AMD. DXGA multi-GPU support stands on its own two legs. All that the vendor needs is to make sure their hardware and software match the multi-GPU features that are in DirectX 12. This is why AMD does not call multi-GPU support in its latest CrossFire driver release, as it simply does not. No longer.