G-SYNC 101: G-SYNC Fullscreen vs. Borderless/Windowed


DWM Woes?

Requested by swarna in the Blur Busters Forums, is a scenario that investigates the effects of the DWM (Desktop Windows Manager, “Aero” in Windows 7) on G-SYNC in borderless and windowed mode.

Unlike exclusive fullscreen, which bypasses the DWM composition entirely, borderless and windowed mode rely on the DWM, which, due to its framebuffer, adds 1 frame of delay. The DWM can’t be disabled in Windows 10, and uses it’s own form of triple buffer V-SYNC (very similar to Fast Sync) that overrides all standard syncing solutions when borderless or windowed mode are in use.

To make sure this was the case, all combinations of NVCP and in-game V-SYNC, as well as the Windows 10 “Game Mode” and “fullscreen optimization” settings were tested to see if DWM could be disabled, and tearing could be introduced; it could not be, so Game Mode and fullscreen optimizations were disabled once again, and NVCP V-SYNC was re-enabled across scenarios for consistency’s sake.

The question is, does DWM add 1 frame of delay with G-SYNC using borderless and windowed mode?

Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings

Overwatch, shows that, no, with G-SYNC enabled, both borderless and windowed mode do not add 1 frame of delay over exclusive fullscreen. Standalone “V-SYNC,” however, does show the expected 1 frame of delay.

CS:GO was also tested for corroboration, and ought to have the same results, as DWM behavior is at the OS-level and should remain unchanged, regardless of the game…

Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings

Sure enough, again, G-SYNC sees no added delay, and V-SYNC sees the expected 1 frame of delay.

Further testing may be required, but it appears on the latest public build of Windows 10 with out-of-the-box settings (with or without “Game Mode”), G-SYNC somehow bypasses the 1 frame of delay added by the DWM. That said, I still don’t suggest borderless or windowed mode over exclusive fullscreen due to the 3-5% decrease in performance, but if these findings are true across configurations, it great news for games that only offer a borderless windowed option, or for multitaskers with secondary monitors.



220 Comments For “G-SYNC 101”

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Sort by:   newest | oldest | most liked
gen36
Member
gen36

Hi, I have a question about limiting frame rate at (refresh rate – 3).

My understanding is that if FPS > refresh rate, GSYNC defaults to VSYNC behavior (if VSYNC is enabled in Nvidia CP), which can result in additional input lag.

But I have some confusion on this. Example scenario:

– 144 Hz monitor.
– I’m playing an undemanding game, VSYNC OFF, and get 200 FPS.
– I turn on GSYNC + VSYNC, and get 144 FPS.
– With GSYNC + VSYNC on, is it defaulting to VSYNC ON behavior? Frame rate is not exceeding refresh rate but *would have* if vsync was off.

(My confusion is coming from the section in the FAQ saying if your frame rate exceeds refresh rate, to cap at a value lower than refresh rate, but if vsync is on, FPS doesn’t exceed refresh rate anyway)

Silver3
Member
Silver3

I was wondering if you could explain me a very persistent Frametime-Spiking-relating issue I’ve got recently with the console-emulator Cemu that I am tearing my hair out about at this time.

[… original comment modified here for length; view below comment reply for pertinent details w/follow-up…]

Sorry btw for that wall of text, but I am quite at my wit’s end by now on my way comprehending other/similar builds’ success although they probably don’t care half of that, pc-related, the way I do and I seemingly checked all of your mentioned points possibly causing frametime-spikes
and will continue with the hardware-part tomorrow.
If you have any suggestion that merely could hint in a direction I overlooked, PLEASE let me know.

Thank you for reading.

Skwuruhl
Member
Skwuruhl

On the topic of FPS limiters: Two tests have been done somewhat recently that found that RTSS provides more consistent frame times than in-game limiters do (at the expense of 1 frame of input lag)
https://youtu.be/xsXFUVYPIx4
https://www.reddit.com/r/Competitiveoverwatch/comments/9vcxz5/rtss_vs_ingame_fps_cap_or_frame_limit/
What’s your take on these?

rpate124
Member
rpate124

What value should the frame time limit be set to in rtss?

GITS_2501
Member
GITS_2501

Amazingly detailed, thanks for the guide. Is there a difference between having V-SYNC: ON versus VSYNC: Fast?

Thanks heaps.

wpDiscuz