AMD Radeon R9 Fury X review - DirectX 12

Direct X 12 - feature level support

With Windows 10 just around the corner there has been a lot of talk about DirectX 12 support for the AMD refresh graphics cards. DX12 is going to be a massive improvement for PC gaming. The low DX API overhead is going to work wonders in terms of CPU utilization and increased numbers of objects in a 3D scene thanks to that low overhead. Simply put: much more efficient hardware through smarter software! At the discretion of a game developer, this superior efficiency can be spent on higher framerates, lower latency (VR), lower power consumption, better image quality, or some calculated balance of all four. In any scenario, gamers stand to benefit greatly from choosing AMD hardware to run their favorite DirectX 12 game.

AMD Radeon 300 Series Graphics fully support Microsoft DirectX 12, with the following enhancements over earlier products

• Faster Tessellation
• Tiled Resources – Support for massive virtual textures, enabling dynamic loading of tiles into graphics RAM for expansive game world details

AMD does support DirectX 12, but not completely (but neither does Nvidia with the previous-gen products). The current generation GCN based GPUs don’t offer full DirectX 12 support, they are limited to Feature Level 11_1 & 12_0 while the competition with Maxwell have full Feature Level 12_1 support.

Make no mistake though, while the higher feature level is not supported, the most important ones, low API overhead and tiled resource, are supported. For GPUs of this age there thus indeed is proper DX12 support, at the very least for the most important features.

The reference DirectX 12 API (Feature Level 11_0) offers performance aimed features, two other levels offer graphics quality features. Feature level 12_0 comes with Tiled Resources, Typed UAV Access and Bindless Textures support. Feature Level 12_1 has the Raster Order Views, Conservative Raster and Volume Tiled Raster enabled on the API. For AMD this means that their latest cards will support Feature Level 12_0 - NVIDIA’s Maxwell 2.0 architecture (900 series) have support for Feature Level 12_1. AMD cards that feature level 12_ 0 support include cards as old as Radeon HD 7790, Radeon R7 260 (X), Radeon R9 285, Radeon R9 290 (X) and R9 295X2.

AMD's Robert Hallock stated that there’s no problem with not featuring DirectX Feature Level 12_1 support since features are performance enhancing tools which are already available in 11_1 and 12_0 and most games won’t rely on utilization of 12_1. So this is all directly related to the GCN revision, in an overview it would look a little something like this.
 

Multi-GPU and DX12

Previous versions of DirectX did not directly support multi-GPU configurations. Developers designed their own support in games and drivers, but there were often limitations: minimal control over the hardware, restricted GPU combinations, and difficulty optimizing graphics workloads for multiple GPUs. DirectX 12’s explicit multi-adapter adds multi-GPU support to DirectX for the first time, giving game developers a much finer and more direct level of control over PC hardware. This control can enable DirectX 12 game engines to extract more performance from multiple GPUs, and use multi-GPU configurations that were not possible in DirectX 11.

Efficiency on multi-core CPUs
Previous versions of DirectX were not capable of fully utilizing a multi-core CPU like the AMD FX 8-core processor. Much of the graphics API work in a PC game would overload one or two CPU cores, ultimately stifling performance. With DirectX 12, however, the work of a game’s graphics engine can easily be spread over all eight cores, leading to more work done in a shorter amount of time. 

Where's the Crossfire Connector??

The Crossfire bridge we all know and learned to love are phased out. AMD is running Crossfire over the PCI Express bus. Especially with standards like PCI-E Gen 3.0 there's a ton of spare bandwidth there, but even at Gen 2.0, it really should not be an issue. For  cards setup in Crossfire, PCIE Gen 3.0 is recommended. What if you do not have PCI-Epress 3.0 compatibility? Well, the bus will revert to Gen 2.0 which will probably not make more then a marginal difference as it is really hard to flood even two x8 Gen 2.0 ports. BTW, it is a myth that Crossfire with 290X and Fury X cards would not work on Gen 2.0 slots.

PCIe Gen 3

The Radeon Fiji based products are all PCI Express Gen 3 compatible, which provides a 2x faster transfer rate compared to the previous generation, this delivers extra bandwith for next generation of extreme gaming solutions. So opposed to the PCI Express 2.0 slots, the PCI Express Gen 3 will have twice the available bandwidth and that is 32GB/s, improved efficiency and compatibility and as such it will offer better performance for current and next gen PCI Express cards. To make it even more understandable, going from PCIe Gen 2 to Gen 3 doubles the bandwidth available to the add-on cards installed, from 500MB/s per lane to 1GB/s per lane. So a Gen 3 PCI Express x16 slot is capable of offering 16GB/s (or 128Gbit/s) of bandwidth in each direction. That results in 32GB/sec bi-directional bandwidth. You do need a PCI-E 3.0 compatible motherboard and processor though.