Last reply by 07-23-2020 Unsolved
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m15 R3, 30Hz to LG C9 120hz monitor, G-Sync

Hi, so my laptop arrived today (super impressed). There are 3 video output options:
DP 1.4
Thunderbolt 3
HDMI 2.0

My LG C9 TV and can handle 120Hz but only has HDMI I any case I wish to enable G-Sync. It sounds to me Thunderbolt is the best lead but can it handle G-Sync? I know DP already does but wanted to check here first with you awesome guys.

Also I plan to buy a 240Hz monitor in addition too to make full use of the refresh on offer.


Replies (19)
7 Plutonium

@Carl1978  G-Sync has two key requirements.  First, you have to be using DisplayPort (or USB-C/TB3, which uses DisplayPort for video traffic).  And second, you have to be using a port that is wired directly to the system's NVIDIA GPU.  On every Dell system I've seen, the USB-C/TB3 port is wired to the Intel GPU, and the NVIDIA GPU only accelerates content on displays attached that way via NVIDIA Optimus, which means it acts as a "render-only" device that passes completed video frames to the Intel GPU.  That has some battery life advantages, but it prevents using G-Sync, as well as Adaptive V-Sync, VR, stereoscopic 3D, and some other technologies.

However, I believe on that system that the Mini-DP output is wired directly to the NVIDIA GPU, in which case that would be the preferable output.  If you want to verify, connect a display to whichever output(s) you want to test, then open NVIDIA Control Panel and go to the PhysX Configuration section.  In there you'll see a diagram showing which GPU controls each active display.  See how it looks when you have displays connected various ways.

7 Plutonium

@Carl1978  Ok, building on the above, it appears that the 2019 LG OLED models are "G-Sync Compatible" displays, and since they appear not to have any DisplayPort inputs, it appears that NVIDIA has done something to get this running over HDMI.  In that case, if you run the test I mentioned above and find that your HDMI output is wired to your NVIDIA GPU (which seems likely on that system since Dell might have done that to support running HDMI-based VR headsets), then I'd connect via HDMI.  If not, then if you're trying to run high refresh rates, you might have to get an active Mini-DisplayPort to HDMI 2.0 adapter.  The less common passive Mini-DisplayPort to HDMI adapters and cables won't run HDMI 2.0, to my knowledge.  The issue with them is that they rely on the source DisplayPort output supporting "Dual Mode DisplayPort", which allows a DisplayPort output to fall back to native HDMI signaling.  The problem is that DisplayPort existed long before HDMI 2.0 did, so I don't know if that capability will allow the source to send (and therefore the adapter/cable to carry) an HDMI 2.0 signal.  By comparison, an active adapter involves the source system sending a native DisplayPort signal to the adapter and then the adapter converts it to HDMI 2.0.

Also, according to this NVIDIA article, you can only run 120 Hz when you're using QHD resolution.  With 4K you'd be limited to 60 Hz.  That's a limitation of HDMI 2.0 itself.  But that article might help you get everything set up.

7 Plutonium

@Carl1978  Sorry for the triple post here, but this G-Sync support over HDMI in order to operate with these LG TVs came as news to me.  Detailed technical information seems to be scarce, but the articles I've read indicate that a) you are supposed to use the HDMI output on your GPU to use G-Sync with these TVs, and b) this capability is only available with RTX GPUs and GTX 16 Series GPUs.  That's interesting for two reasons.

First, G-Sync in the past only worked over DisplayPort and required the display to have a proprietary G-Sync control board containing pretty powerful components.  Additionally, second, G-Sync has been supported on GeForce GPUs going back well before the RTX and GTX 16 Series GPUs.

So my GUESS here is that the G-Sync in this particular case of the LG OLED TVs isn't the "normal G-Sync" that involves NVIDIA proprietary technology, but rather HDMI VRR or something very much like it.  That might explain both why this LG OLED use case works over HDMI and why it's only possible on NVIDIA's latest GPUs.  But that may also mean that G-Sync to an LG OLED might be possible ONLY from an actual HDMI source port wired directly to the NVIDIA GPU, i.e. the Mini-DisplayPort output might not be usable for G-Sync to an LG OLED TV no matter what type of adapter/cable you use.  So hopefully your HDMI output is wired to the NVIDIA GPU.

As for the 240 Hz display you're considering purchasing, if it supports G-Sync, chances are it will be "normal G-Sync" that operates over DisplayPort, in which case connect it to the Mini-DisplayPort output.


What an absolutely amazing response you have posted!  Honestly I cant thank you enough for this, please have 10x digital drinks on me and very much appreciated kudos!! - here is the screenshot I took of the config I have so far; couldn't quite see the video card showing the connections but does appear to show the Super card linked to the LG via hdmi, which I know is working fine as I just extended my display to it and its been hitting buttery smooth 120fps on ultra settings which then dropped to around once I enabled RTX.....and wow, I am absolutely blown away by this level of gaming!!  RTX is breathtaking, and then all the water droplets and little touches (testing on Shadow of Tomb Raider).

So I have the frames sorted which is lovely, the couple of questions I would have then if I may:

1)  How can I tell if G-sync is working or not?  The laptop I bought, I went for the 300hz one simply because I didn't see the point on getting the 144hz proper g-sync one, I don't see much value in gaming on 15inch vs 55......I did see in the spec that the super cards can output g-sync, I vaguely recall this being via DP though so this is very interesting if its via HDMI.  The hdmi port is actually hdmi 2.1 also, I've read that had I bought the LG CX then id be able to get 4k 120fps via 2.0 as it drops to 4:2:0 colour data (I think).  

2)  Is it possible to game in 2k at all at over 100fps?  Anything outside of 1080 is only showing 60hz, for example 3840 x 2160 is 60hz.  If I look to 2k, 2560 x 1440 its only hitting 30hz.  Ideally I could push for 2k and still hit over 100fps, strange how it would goto 4k and offer 60hz.....

As for the other monitor, a DP 1.4a to hdmi 2 will probably be fine, although.....TB3 would have been nice had gsync worked.  Monitor wise I've managed to find a real 10bit one too, which seems to be a rarity

I'm so excited by all of this.....the gaming experience I just saw then was mind blowing, I mean I've got the Xbox X, the Nvidia shield with geforcenow, I've testing ultra settings before but its capped at 60fps and I'm not sure why but this seems leagues above the geforcenow experience!  No way will I be using that again 

I'm very much new but keen to learn......I notice there are a lot of settings too which is a little confusing ranging from the nvidia settings to the ingame settings.....

I suffer from eye strain, but need to take care of eye comfort which is why Ive invested in better screen tech, ie there is no colour dithering going on anywhere, the LG is a pure 10bit panel, my laptop is 100% sRGB, there isn't much more I can do, but all that aside I feel like a kid in a candy shop, all I need to do now is learn to code and I'll be away!


Okay so this has become more interesting! :). - so I selected a 4k display, it then did something really funky and switched back to laptop/LG screens on at the same time, duplicate mode, but the laptop was all purple tinge.  Then I noticed the g-sync options appeared and was labelling the LG monitor differently, now it will allow me to select 4k at 60hz, but gsync is enabled so at least I will know that's working.  Just puzzled to why there isn't a 2k option better than 30hz...and quite amazed this is all working over hdmi so far. here is the gsync options
if I have the laptop only this is the only resolution you can get


@Carl1978  Happy to help. I'll try to address some of your follow-up questions and clarify a few things:

Your screenshot: The screenshot you posted clearly shows the active external display (surprisingly) even the laptop's built-in display both controlled by the NVIDIA GPU.  I guess this system might be wired that way in order to support the G-Sync built-in display option it offers.  I'm not sure what you mean by saying you couldn't quite see the video card connections.  They're right there in that diagram.  But the important part is that the line from your display goes to the gray box that corresponds to your NVIDIA GPU.  And since there isn't even an Intel GPU shown at all, I suppose it's possible that even the USB-C/TB3 video output is wired to the NVIDIA GPU, although even if that's the case, it won't necessarily be any better -- in fact the specs indicate it may be worse.  According to Dell's product page, the USB-C/TB3 port only supports DisplayPort 1.2, whereas the Mini-DisplayPort output supports DisplayPort 1.4.  Of course whether that makes a practical difference depends on what display(s) you connect to those interfaces, but I wouldn't feel too disappointed about not being able to use USB-C/TB3.

G-Sync and your built-in display: The NVIDIA article I linked shows how to enable G-Sync.  If you successfully enable it as shown in that article, then it's working.  As for your built-in display, I would have gone with 144 Hz G-Sync rather than 300 Hz seeing as the latter seems not to allow G-Sync.  For one thing, whether the human eye can even detect anything beyond 144 Hz is dubious at best.  Even hardcore competitive gamers seem to find that 120 Hz is plenty.  But much more importantly, running a high refresh rate without the benefit of G-Sync can actually be a much worse experience overall.  The reason is that without G-Sync, your options are either V-Sync Off or V-Sync On.  Running V-Sync Off means you can experience frame tearing, since that's precisely what V-Sync was created to solve.  V-Sync On solves that problem, but it does so by ensuring that the GPU only sends a video frame when the display is ready to refresh.  The issue there is that it means the GPU has to sustain a frame rate at least as high as the display's refresh rate, i.e. with a 300 Hz display you'd need to sustain 300 fps, which is obviously a pretty tall order.  When the GPU's frame rate drops below the display's refresh rate, i.e. it doesn't have the next video frame ready for the display's next refresh cycle, then it will "buy time" by simply repeating the last frame -- which you perceive as stuttering or judder-y motion, and lag.  This is precisely the dilemma that G-Sync was created to solve.  It avoids frame tearing WITHOUT introducing the potential for this motion/lag issue by allowing the refresh rate of the display to adapt dynamically to the frame rate the GPU can sustain at any given time.  In that case, your display's refresh rate is its MAX refresh rate, not its fixed refresh rate, which removes the risk.  But if you don't have G-Sync, you don't have that option.

Gaming at "2K": First of all, "2K" is a bad term to use for display resolutions.  2K is technically a film resolution of 2048x1080, and therefore when applied in the consumer space it actually is SUPPOSED to refer to the nearest and slightly LOWER resolution of 1920x1080.  Similarly, "4K" is a film resolution of 4096x2160, but when used in the consumer space it refers to 3840x2160.  Somehow using 2K to refer to 2560x1440 came into vogue, but it's wrong, and the ambiguity about what a person actually means when they say "2K" can cause confusion that might lead people down the wrong path when troubleshooting something for example.  2560x1440 is rightfully called "QHD" or "1440p".  The former is only one extra character to type, but it adds a lot of disambiguation value.   In terms of whether 100 fps gaming at QHD is possible, it depends on the game and your detail settings.  But with modern games at detail settings you'd probably want to run, that would probably be a stretch for any gaming laptop, even a new M15 R3.  But you're also using FPS and Hz interchangeably in your question here.  The frame rate the GPU can achieve is not necessarily linked to the refresh rate of the signal it's sending to the attached display.  You're limited to 60 Hz at 4K resolution because that's what your display supports, because that's all HDMI 2.0 supports (same for DisplayPort 1.2).  But your GPU might still be able to render frames more quickly, or more slowly, depending on the complexity of what it's rendering.  Technologies like V-Sync and G-Sync determine how the rendered frames "map" onto refresh cycles of the display itself.

I don't know why you'd want a DP 1.4 to HDMI 2.0 for "the other display".  If you're getting a 240 Hz display, the overwhelming likelihood is that it will have a DisplayPort input.  It will probably be full-size DP rather than MiniDP, but in that case keep it simple and get a MiniDP to DP cable/adapter and call it a day.  There's no point adding active adapters into the mix when they're not needed.  That's just extra cost and complexity that is completely avoidable.

Being "capped" at 60 fps could be the result of using G-Sync or V-Sync.  If you have either of those, then the GPU won't render at a frame rat higher than the display's refresh rate.


@Carl1978  It seems you wrote another reply while I was posting my own.  I'm not sure why you're limited to 30 Hz when selecting QHD, particularly as the NVIDIA article I linked that specifically deals with your TV suggests that you should be able to run 120 Hz.  Maybe confirm you're running the latest firmware and NVIDIA drivers?


@Carl1978  Just saw that other screenshot too.  QHD (2560x1440) isn't even listed in your resolution choices, at least not within the portion of the list that's visible in your screenshot.  2560x1600 is, but that's not the same thing.  However, comparing that against the screenshot in the NVIDIA article I linked, 2560x1440 is at the very bottom in the PC resolution section, not the "UltraHD,HD,SD" section.  So maybe scroll down your resolution list to see if you have 2560x1440 at the very bottom somewhere.  And if you do, see if you can enable 120 Hz.


Hi again,

I've just noticed your reply again, thanks once more.  This is just a follow up on trying to get past 30fps, it was set on the laptop to 4k but in the game it was 1080p still, I adjusted to 4k, and also the 1440 on also, both were still on 30fps, id be happy to get the higher fps with a higher resolution on a 55 inch screen.  

I've not read your reply yet but I will first thing in the morning, I did see about g-sync and the 144hz, maybe it might have been a better option from that pov, that said with gsync working I'm guessing that's less of a problem as I dont intend to game just on the laptop screen itself.  The higher refresh was more for the sake of my eyes, can't explain why but higher refresh just seems to cause less eye fatigue.

Look forward to picking this up in the morning, appreciated again

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