NVIDIA Reflex Low Latency - How It Works & Why You Want To Use It

[jorimt]

I am trying to accomplish to minimize input lag and not having tearing. I can see that you did the test with 60 Hz and having quite significant improvements when not capping your FPS. But what when doing it with a higher refresh rate of e.g. 144 Hz? I think the improvements in terms of latency between V-SYNC (NVCP) ON and OFF while using Reflex would be way less?

Are you intending to use VRR or standalone V-SYNC to prevent tearing? Because my answers will differ depending on that; it's all highly relative.

[marcel151]

If understood correctly it should be VRR. Right now I am using G-SYNC plus Reflex if available (otherwise capping 3 FPS under refresh rate in game). V-SYNC is off in game and on in NVCP. I am thinking about turning V-SYNC off in NVCP when using very high FPS games.

[jorimt]

If understood correctly it should be VRR. Right now I am using G-SYNC plus Reflex if available (otherwise capping 3 FPS under refresh rate in game). V-SYNC is off in game and on in NVCP. I am thinking about turning V-SYNC off in NVCP when using very high FPS games.

Okay, not sure what else to add beside...

Lowest possible tear-free latency:
G-SYNC on + V-SYNC on + minimum -3 FPS within the refresh rate + GPU usage below 99% (via Reflex or a manual FPS limit)

Lowest possible latency (with tearing):
G-SYNC off + V-SYNC off + highest possible framerate without causing GPU usage to reach or exceed 99% (via Reflex or manual FPS limit)

[pt0x]

If understood correctly it should be VRR. Right now I am using G-SYNC plus Reflex if available (otherwise capping 3 FPS under refresh rate in game). V-SYNC is off in game and on in NVCP. I am thinking about turning V-SYNC off in NVCP when using very high FPS games.

Okay, not sure what else to add beside...

Lowest possible tear-free latency:
G-SYNC on + V-SYNC on + minimum -3 FPS within the refresh rate + GPU usage below 99% (via Reflex or a manual FPS limit)

Lowest possible latency (with tearing):
G-SYNC off + V-SYNC off + highest possible framerate without causing GPU usage to reach or exceed 99% (via Reflex or manual FPS limit)

Hi there,

Even though I think these settings and the statement itself are correct I still struggle to believe it, even with reflex involved. Why? Hear me out, this is somewhat of a question/reflection at the same time.

In scenario 1, the only system latency inducing factor would be a GPU or CPU bound scenario for the choosen FPS limit. Reflex can assist with this, and drop latency by alot, when the GPU and CPU are not bound, the render queue is empty, frame processing doesnt need to be synced by reflex and you might actually get lower system latency with reflex off.

Typically in overwatch 2 on a 14900k, 4090 and 240hz monitor with g-sync, v-sync and in game frame cap of 234 I have 4.8ms system latency as its not bound by anything.

With g-sync, v-sync and reflex on my fps get capped to 225~ by reflex and my system latency is 5.9. So I rather leave relex off for this game.

In scenario 2, I can't deny the simple truths of more frames = less latency... but... how about the devation between frames, that rises so much in some games that going for this scenario realy is not usefull as latency fluctuates too much and therefore creates a system latency avarage that is simply not relyable or consistant. Yeah the numbers might show 2ms, but the devation is more important imho. Plus, you will have frame tearing, which can be less clear, possibly inducing more latency at the human.

My statement has always been. (And pleae correct me if im wrong)!

"If you already have low latency in the first place, dont uncap fps and choose no screen tearing + stable frame pacing"

Like in my example

[jorimt]

I said "lowest possible latency," not "highest possible consistency." And you don't have to use Reflex to prevent max GPU usage, you can use a manual FPS limit instead.

[Kook]

Hey Yall. I know this forum has been quiet for a while but I’ve been tinkering with my settings and I really need guidance. I have an RTX 4070 GPU, 32GB Ram, 1TB SSD, 13 Gen 13700 CPU.

I have a 165hz Freesync monitor and I got a DP cable which allows me to turn on gsync. I’ve followed your guide of capping my frames (3-5 below the refresh rate) at 160 in nvcp. I’ve also turned on vsync in NVCP and off vsync in game. I also set reflex to ON option in CS2 and I’ve noticed that my frames keep fluctuating and aren’t stable. I’ve tried tweaking with other settings such as HAGS and I’m still having issues. I want to have a tear free experience while maintaining low latency.

I play on faceit and they don’t allow RTSS as it needs a special console command. Should I turn off reflex? Should I turn HAGS back on? Should I disable the frame capper or set the frame capper at 155 (3 below the reflex auto cap)? Please I’ve spent a lot of time reading your forums and I just feel lost.

Please help me out and if you have any questions I would be willing to answer them

[jorimt]

I’ve noticed that my frames keep fluctuating and aren’t stable.

Frametime, framerate or both?

Because my minimum -3 FPS limit is only to ensure the framerate doesn't exceed the refresh rate so VRR remains engaged, it does not guarantee average framerate consistency.

So if all you're looking to achieve is a consistent framerate (say you want a constant 90 FPS instead of a fluctuating 90-160 FPS), then you simply need to find your lowest achievable average framerate in CS2 (at your chosen graphical settings), and then manually limit just below it. This will give you a near constant average framerate and should reduce frametime variance, but it will, of course, not fix frametime spikes or netcode-related issues.

I’ve tried tweaking with other settings such as HAGS and I’m still having issues.

In my experience, HAGS may cause more GPU-side stutter in some scenarios, but it can vary by game/API.

I want to have a tear free experience while maintaining low latency.

G-SYNC + NVCP V-SYNC + a framerate within the refresh rate that avoids 99%+ GPU usage (be it with a manual limit or Reflex) is the lowest tear-free latency possible.

Should I turn off reflex?

With G-SYNC + V-SYNC, Reflex does two things; 1) sets an automatic limit slightly below the physical refresh rate to keep VRR active, and 2) it dynamically monitors GPU usage, so whenever usage reaches/exceeds 99%, Reflex dynamically limits the framerate just below that to prevent extra render queue latency.

You can also achieve both #1 and #2 with an external or in-game limiter, you simply have to do so manually, #2 of which can be difficult to tune for if your system can't easily sustain a consistent average framerate.

[Kook]

Oh okay thanks Jormit!

So If I use a NVCP frame cap at 158 (automatic cap by reflex) and disable reflex would I achieve the same latency?

Also is it better to use NULL ultra or a frame cap in combination with reflex if I decided to use reflex?

Do you recommend I use the On or Boost option? I heard On is safer than boost.

If I’m using reflex to cap my frames what should I set my in game frame cap to? (0?)


What do you recommend setting the shader cache size, image scaling (gpu vs display debate) in the NVCP? Or does it not matter that much?

Sorry for all the questions but I’m intrigued in learning from you. Thanks

[jorimt]

So If I use a NVCP frame cap at 158 (automatic cap by reflex) and disable reflex would I achieve the same latency?

No, because the NVCP limiter is driver-level, and the in-game Reflex limiter is engine-level. The NVCP limiter will typically have anywhere between 1/2 and 1 1/2 frames of additional latency over an in-game limiter.

Also is it better to use NULL ultra or a frame cap in combination with reflex if I decided to use reflex?

Reflex is superior to LLM and considered it's replacement. When Reflex is enabled, it overrides LLM, regardless of what LLM is set to in the NVCP.

Do you recommend I use the On or Boost option? I heard On is safer than boost.

"Boost" is essentially Reflex + Prefer maximum performance. That's it.

If I’m using reflex to cap my frames what should I set my in game frame cap to? (0?)

Depends.

You want the in-game limit to override the Reflex auto limit, you set it below the Reflex limit. You want the in-game limit not to take effect, you disable it, where possible, or set it higher than the Reflex auto limit.

The lower limit will always take effect over the higher one.

What do you recommend setting the shader cache size, image scaling (gpu vs display debate) in the NVCP? Or does it not matter that much?

Neither of those are directly related to the latency in this particular context.