Following the initial announcement of ntsync kernel driver support in SteamOS 3.7.20 beta, early testing shows minor performance improvements for older Windows games like classic Call of Duty titles running via Proton on the Steam Deck, building on the existing fsync driver.
Valve's SteamOS 3.7.20 beta, highlighted initially by Phoronix on January 9, added kernel-level ntsync support on January 8 to enhance Windows game performance under Proton on Linux devices like the Steam Deck.
While fsync already provides synchronization benefits, ntsync targets compatibility issues in older titles, particularly early 2000s games. Community focus has been on the Call of Duty series, including Call of Duty 4: Modern Warfare and Call of Duty: Black Ops, which previously experienced hitches, framerate drops, and glitches.
Journalist Joshua Brown's tests on a Steam Deck OLED (unplugged) in CoD4's campaign showed fsync-Proton at 130-140 fps, improving slightly to 135-144 fps with ntsync-enabled Proton-GE—stabilizing output near the device's refresh rate cap. Reddit user Sjknight413 reported fixing 'horrendous framerate drops' and visual glitches in Black Ops using the same setup.
Users can access the beta via the SteamOS 3.7.20 branch and install Proton-GE with ntsync via Proton Up-Qt in the Discover store. Though gains are modest, ntsync expands retro PC game viability on portable Linux hardware, with more benchmarks anticipated.