Why is it important: Someone at Valve recently posted an update on how Vulkan on Radeon graphics cards handles VRS to save power. While the update is for Steam Deck, it could also benefit PC.
Valve’s Samuel Pituise has modified the Radeon Vulkan (RADV) driver to provide more control over how variable rate shading (VRS) works. Phoronics notes that a higher degree of control can relate whether the Steam Deck is running on battery power or connected to AC power.
Microsoft introduced VRS for DirectX 12 in 2019 as a performance saving feature. Basically, it can force the game to render different parts of the screen with different levels of clarity and fidelity depending on how important they are. Someone playing a racing game doesn’t necessarily look at the landscape or the sky most of the time, so VRS can make the game spend less effort on pixels in those areas than it does on a car, cockpit, or road.
This feature is supposed to degrade performance on pixels that players won’t notice, such as things obscured by motion blur or pure black pixels inside shadows. Something like this can be critical for a battery powered portable PC like the Steam Deck.
Pituacet’s changes make it possible to dynamically scale VRS rates, and this speed can now be written to a new configuration file. AMD Van Gogh APUs on Steam Deck enable this by default. While Pituise confirmed that this change is intended to save power, Phoronix suggests that this could allow VRS speed to change between different settings when the Steam Deck is running on AC power or on battery power. In theory, this could also have implications for other AMD devices running Vulkan applications.
Late last summer, Valve and AMD collaborated on a new Linux processor driver to improve performance. Any PC with Zen 2 can benefit from this. Around the same time, Valve announced changes to the Steam Big Picture user interface, designed for Steam Deck but also applicable to full PCs.
Steam Deck will start shipping on February 28th.