[Manuel Calavera]

Don’ts

• Don’t rely on the driver to parallelize any Direct3D12 works in driver threads
  • On DX11 the driver does farm off asynchronous tasks to driver worker threads where possible – this doesn’t happen anymore under DX12
  • While the total cost of work submission in DX12 has been reduced, the amount of work measured on the application’s thread may be larger due to the loss of driver threading. The more efficiently one can use parallel hardware cores of the CPU to submit work in parallel, the more benefit in terms of draw call submission performance can be expected.

To se pretpostavljam odnosi na ovo od ashes benchmarka

Curiously, their driver reported this feature was functional but attempting to use it was an unmitigated disaster in terms of performance and conformance so we shut it down on their hardware. As far as I know, Maxwell doesn’t really have Async Compute so I don’t know why their driver was trying to expose that.

analiza

nVIDIA, on the other hand, does much better at Serial scheduling of work loads (when you consider that anything prior to Maxwell 2 is limited to Serial Scheduling rather than Parallel Scheduling). DirectX 11 is suited for Serial Scheduling therefore naturally nVIDIA has an advantage under DirectX 11.

People wondering why Nvidia is doing a bit better in DX11 than DX12. That's because Nvidia optimized their DX11 path in their drivers for Ashes of the Singularity. With DX12 there are no tangible driver optimizations because the Game Engine speaks almost directly to the Graphics Hardware. So none were made. Nvidia is at the mercy of the programmers talents as well as their own Maxwell architectures thread parallelism performance under DX12. The Devellopers programmed for thread parallelism in Ashes of the Singularity in order to be able to better draw all those objects on the screen. Therefore what were seeing with the Nvidia numbers is the Nvidia draw call bottleneck showing up under DX12. Nvidia works around this with its own optimizations in DX11 by prioritizing workloads and replacing shaders. Yes, the nVIDIA driver contains a compiler which re-compiles and replaces shaders which are not fine tuned to their architecture on a per game basis. NVidia's driver is also Multi-Threaded, making use of the idling CPU cores in order to recompile/replace shaders. The work nVIDIA does in software, under DX11, is the work AMD do in Hardware, under DX12, with their Asynchronous Compute Engines.

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PS. Don't count on better Direct X 12 drivers from nVIDIA. DirectX 12 is closer to Metal and it's all on the developer to make efficient use of both nVIDIA and AMDs architectures.