Far from being a beneficial function to balance performance and battery life, the framerate limiter inside the Steam Deck reportedly increases the input latency substantially. A Redditor accidentally stumbled upon the framerate limiter's malfunction while testing the latency between his wireless PlayStation 5 controller and docked Steam Deck. Other Redditors have pitched in on the testing and confirmed the issue.
The amount of input latency scales linearly according to the frame rate and refresh rate cap. For reference, the uncapped input latency is 31.8ms. Enforcing a 30 FPS cap increased to 145.9ms, more than 4X higher. According to the Redditor's results, the worst configuration was the 40 Hz, 20 FPS setting, causing the input latency to skyrocket to 232ms, over 7X more than the uncapped setting. The two settings with the minor input latency penalty are the 50 Hz or 40 Hz uncapped scenario, where the increase was less than 8%.
The Redditor conducted the tests in Rogue Legacy 2 at the settings menu with the Steam Deck undocked. His methodology included using an iOS application called "Is It Snappy?" that essentially captures video at 240 FPS and allows users to set a starting point and endpoint pin to calculate the difference in milliseconds. The Redditor established the starting point when he fully pressed down on the button, and the endpoint was when the screen changed. The user highlighted a margin of error of 4ms, so he averaged the five individual timings from his test runs.
Framerate Limiter Performance
|60 FPS cap||75.8ms|
|30 FPS cap||145.9ms|
|50 Hz / Uncapped||32.5ms|
|50 Hz / 50 FPS cap||94.2ms|
|50 Hz / 25 FPS cap||186.1ms|
|40 Hz / Uncapped||34.2ms|
|400 Hz / 40 FPS cap||121.1ms|
|50 Hz / 20 FPS cap||232.0ms|
In his experiment with Rocket League, the Redditor discovered a minimal to zero increase in input latency. Rocket League is one of those few titles with a built-in framerate limiter (not to be confused with V-Sync). For this experiment, the Redditor configured the target frame rate in Rocket League and the Steam Deck's refresh rate to 50 Hz.
Until Valve issues a fix for the Steam Deck's framerate limiter, the best course of action is to use the game's built-in framerate limiter to match your desired refresh rate on the Steam Deck or leave the latter uncapped. The problem is that not every title has an in-game framerate limiter. Furthermore, the Redditor highlighted he still experienced screen tearing and judder despite using Rocket League's internal framerate limiter.
The Redditor praised the Steam Deck's button-to-photon latency compared to other consoles in other news. The user recorded values between 70ms to 86ms for the Nintendo Switch a year ago, with latency performance similar to the PlayStation 5 or Xbox Series X. However, the Steam Deck (31.8ms) flaunts excellent input latency when uncapped. The only good news is that Valve has delayed Steam Deck pre-orders to after Q3, so it's more than enough time for Valve to fix the issue before the consoles get into gamers' hands. Unfortunately, existing Steam Deck owners will have to use the workaround until an official patch arrives.