The GPU Upload Heaps feature introduced in the Agility SDK version 1.710.0 of DirectX 12 allows the CPU to directly access the GPU VRAM. An interesting novelty that promises a performance boost in video games.
Microsoft announced today the addition of a new functionality within the DirectX 12 API: GPU Upload HeapsWho allows the CPU to directly access the VRAM of the GPU. This new feature appears in the Agility SDK version 1.710.0, alongside non-normalized sampling.
DirectX 12 API Gets Brand New Features Allowing GPUs and CPUs to Directly Access Memory Simultaneously
Historically, a GPU’s VRAM was inaccessible to the CPU, forcing programs to copy large amounts of data to the GPU over the PCI bus. Most modern GPUs have introduced the VRAM Resizable Base Address Register (BAR) allowing Windows to manage GPU VRAM in WDDM 2.0 or later.
The new GPU Upload Heaps feature introduced in the Agility SDK version 1.710.0 of DirectX 12 allows the CPU to directly access the GPU’s VRAM, removing the need to copy data from the CPU to the GPU. This feature is particularly interesting because it improves performance in certain scenarios by reducing data transfers between CPU/GPU and DRAM/VRAM. However, the concrete performance implications are still unknown and will need to be investigated further.
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The prerequisite to take advantage of this feature on the client side is rBAR support, which is provided from 10th Gen Intel Cores and Ryzen 3000s on the CPU side, Radeon RX 5000s and GeForce RTX 3000s on the GPU side. Developers can already use this feature, which is supported by NVIDIA and Intel drivers (Game Ready driver version 531.41 and Intel driver 31.0.101.4255 or newer). For AMD GPUs, developers must request a special driver from the company.
It is important to note, however, that this feature has only just been launched by Microsoft (March 30, 2023), so it will be some time before we see its implementation in games.
Source : Microsoft
