Question Display Limits for CPU or GPU issue?

[FrequentFlyer]

Hello,

I have a setup that includes 11 overall displays, all are 1920 * 1080 besides a couple that are 1920*1200 and one 4k tv. These displays are connected to four GTX 1080 cards and the CPU is an Intel Core i7-7700 both of which I believe are slightly overclocked. The issue is that we are running into major framerate issues when we use all of the screens (flight simulation), which in my opinion is understandable as I don't think our CPU is capable of supporting so many displays. Looking at the specs for the CPU it says it supports a max of 3 displays, however it definitely runs like 4-5 just fine. I was thinking the # of displays on that CPU is definitely bottlenecking our system's performance. So my questions are: 1. Do you think I am fairly correct about the CPU? 2. If so, would an Intel Core i9-9920x or something similar and more new be a better fit? 3. Or completely different, am I having a GPU issue?

Thanks!

 

[-Fran-]

The CPU has zero saying in how many displays you can have. The maximum display amount is always given by the GPU (RAMDAC/TMDS in particular) and what it's capable of driving in terms of resolution (each screen takes some MB's from memory) and processing (each screen takes a chunk of GPU time to display and render stuff).

Games in particular can have support for certain resolutions, but it's always the GPU's job to fit them to any arbitrary number of screen and their individual resolutions and refresh rates.

Unless it's officially stated by the OEM or even nVidia, each GPU has a theoretical upper limit in terms of display (and resolution+refresh) numbers and a practical limit for games.

Cheers!

 

[FrequentFlyer]

Why would the i7-7700 specs say "# of Displays Supported =3 " then? More displays = more necessary computing power, because not all of it falls upon the GPU, well the graphics side does but that results in more information needing to be processed by the CPU. For such a big setup I honestly don't have a clue as this is very complicated, but those are my thoughts. Let me know what you think.

 

[digitalgriffin]

Hello,

I have a setup that includes 11 overall displays, all are 1920 * 1080 besides a couple that are 1920*1200 and one 4k tv. These displays are connected to four GTX 1080 cards and the CPU is an Intel Core i7-7700 both of which I believe are slightly overclocked. The issue is that we are running into major framerate issues when we use all of the screens (flight simulation), which in my opinion is understandable as I don't think our CPU is capable of supporting so many displays. Looking at the specs for the CPU it says it supports a max of 3 displays, however it definitely runs like 4-5 just fine. I was thinking the # of displays on that CPU is definitely bottlenecking our system's performance. So my questions are: 1. Do you think I am fairly correct about the CPU? 2. If so, would an Intel Core i9-9920x or something similar and more new be a better fit? 3. Or completely different, am I having a GPU issue?

Thanks!

It's the raw number of pixels you are pushing if you are extending all the displays. You're GPU limited for sure in your flight sim.

 

[digitalgriffin]

Why would the i7-7700 specs say "# of Displays Supported =3 " then? More displays = more necessary computing power, because not all of it falls upon the GPU, well the graphics side does but that results in more information needing to be processed by the CPU. For such a big setup I honestly don't have a clue as this is very complicated, but those are my thoughts. Let me know what you think.

The i7-7700 has it's own iGPU. The CPU pin outs support VGA, DVI/HDMI, DP usually. That's your 3 displays. So the CPU is referring to it's own display capabilities, not the display capabilities of the video card on the PCIe bus.

 

[-Fran-]

Why would the i7-7700 specs say "# of Displays Supported =3 " then? More displays = more necessary computing power, because not all of it falls upon the GPU, well the graphics side does but that results in more information needing to be processed by the CPU. For such a big setup I honestly don't have a clue as this is very complicated, but those are my thoughts. Let me know what you think.

As @digitalgriffin already said, it's because Intel doesn't call their CPU+iGPU "APU"s like AMD does, so it's harder to explain to average joe their CPUs come with an integrated GPU.

And like I said, that is defined by what Intel considers their iGPU can handle because of processing capabilities, drivers or lazyness of specs (most businesses just make do with 3 screens tops before using discrete GPUs).

Cheers!

 

[FrequentFlyer]

It's the raw number of pixels you are pushing if you are extending all the displays. You're GPU limited for sure in your flight sim.

Yikes. Not what I really wanted to hear. I never would have thought 3 GTX 1080s supporting 3 displays each and 1 GTX 1080 supporting 2 displays would be an issue at all. So if I upgraded to four Titan Xs I should get better performance?

Additionally, I know what screens are run on each graphics card and if I only run the simulation on a certain screens (1 GPU) there doesn't seem to be a frame rate issue. How can that be? That just doens't make sense to me. Or even 4 separate GPUs running 1 screen each at the time doesn't give me an issue.

Thanks for your help.

 

[-Fran-]

Yikes. Not what I really wanted to hear. I never would have thought 3 GTX 1080s supporting 3 displays each and 1 GTX 1080 supporting 2 displays would be an issue at all. So if I upgraded to four Titan Xs I should get better performance?

Additionally, I know what screens are run on each graphics card and if I only run the simulation on a certain screens (1 GPU) there doesn't seem to be a frame rate issue. How can that be? That just doens't make sense to me. Or even 4 separate GPUs running 1 screen each at the time doesn't give me an issue.

Thanks for your help.

Usually it's professional cards that can drive an insane amount of displays or specialized cards (good ol' Matrox) to such ends.

https://www.anandtech.com/show/1460...-3200-a-professional-graphics-card-for-sub200

Consumer grade cards are normally fine with driving 3-4 displays at once while some exceptions lurk around. Particularly from AMD, as they're usually capable of running 6 1080p displays with no problems when you can use DVI/DP splits.

Cheers!

 

[digitalgriffin]

Yikes. Not what I really wanted to hear. I never would have thought 3 GTX 1080s supporting 3 displays each and 1 GTX 1080 supporting 2 displays would be an issue at all. So if I upgraded to four Titan Xs I should get better performance?

Additionally, I know what screens are run on each graphics card and if I only run the simulation on a certain screens (1 GPU) there doesn't seem to be a frame rate issue. How can that be? That just doens't make sense to me. Or even 4 separate GPUs running 1 screen each at the time doesn't give me an issue.

Thanks for your help.

head bang Your software would have to support 4 card SLI setup. There are NO consumer commercial software applications running 4 cards setups in SLI I know of. Someone chime in if I'm wrong.

So what happens is when DirectX* starts up, it enumerate (or list) the cards to the program. The program then has to pick out WHICH SINGLE CARD to render too. (Unless a SLI setup exists) So what is likely happening is your single card is doing the rendering and then stitching it across multiple displays using NVIEW.

The way to confirm this is run something like GPU-Z and look at the usage rates of all your cards.

To be honest you would be way better off wearing a VR helmet. There are flight sims that do support these.

*(I'm guessing DirectX is what your flight sim is using)

 

[-Fran-]

head bang Your software would have to support 4 card SLI setup. There are NO consumer commercial software applications running 4 cards setups in SLI I know of. Someone chime in if I'm wrong.

So what happens is when Direct X (I'm guessing this is what your flight sim is using) starts up, it enumerate (or list) the cards to the program. The program then has to pick out WHICH SINGLE CARD to render too. (Unless a SLI setup exists) So what is likely happening is your single card is doing the rendering and then stitching it across multiple displays using NVIEW.

The way to confirm this is run something like GPU-Z and look at the usage rates of all your cards.

To be honest you would be way better off wearing a VR helmet. There are flight sims that do support these.

That's a more complex can of worms, but you can simplify it a bit with:
1.- The driver can make the whole GPU arrangement look like one GPU block/blob (think Virtu, for instance or other "masking" software/driver). SLI or XFire is just a technique to fool the system into thinking it's dealing with 1 GPU (with some caveats; hence the can of worms).
2.- With Vulkan and DX12 you can access each card individually as long as the driver expose them as such. This will rely on 100% on how the software writers did their thing, clearly (hence, again, the can of worms).

Cheers!

 

[FrequentFlyer]

head bang Your software would have to support 4 card SLI setup. There are NO consumer commercial software applications running 4 cards setups in SLI I know of. Someone chime in if I'm wrong.

So what happens is when DirectX* starts up, it enumerate (or list) the cards to the program. The program then has to pick out WHICH SINGLE CARD to render too. (Unless a SLI setup exists) So what is likely happening is your single card is doing the rendering and then stitching it across multiple displays using NVIEW.

The way to confirm this is run something like GPU-Z and look at the usage rates of all your cards.

To be honest you would be way better off wearing a VR helmet. There are flight sims that do support these.

*(I'm guessing DirectX is what your flight sim is using)

If this is correct, I am honestly laughing right now. I did not build this setup and am only in charge of increasing the performance. So even though it says it is running each set of screens from each specified GPU from the NVIDIA control panel, it actually might not be? Just clarifying something that really doesn't need clarifying but I am in awe.

We additionally do have VR equipment but don't want that to be it's only use, especially when you can't see buttons in the cockpit.

 

[FrequentFlyer]

Generically, would I be better off with one very powerful and expensive GPU? I think you mentioned that.

 

[-Fran-]

Not necessarily... A single powerful GPU solves a lot of problems, yes, but does not mean necessarily is what you're looking for.

If you're doing CAD work or CUDA related stuff, multi-GPU might be better still.

Games though, yes. Single GPU is less of a pain and keeps things simple.

Cheers!

 

[FrequentFlyer]

Not necessarily... A single powerful GPU solves a lot of problems, yes, but does not mean necessarily is what you're looking for.

If you're doing CAD work or CUDA related stuff, multi-GPU might be better still.

Games though, yes. Single GPU is less of a pain and keeps things simple.

Cheers!

We use Prepar3d, basically a game just with flight simulation. Is there a good one I can get for 11 displays? Although one of them is 4k... so that may be an issue.

 

[digitalgriffin]

We use Prepar3d, basically a game just with flight simulation. Is there a good one I can get for 11 displays? Although one of them is 4k... so that may be an issue.

You'll need to contact Lockheed Martin and see if they support such setups directly.

But you are simply expecting too much. Even the best/fastest cards today have problems rendering 4K @ 60fps. The fact you are trying to render to more than 1 is nothing short of insane. Whomever set this system up didn't know what they were doing.

 

[FrequentFlyer]

You'll need to contact Lockheed Martin and see if they support such setups directly.

LOL. Have emailed them non stop back and forth for 4 months and they are useless which is why I came here. Maybe another 4 months, they'll finally give me a recommendation which I have found that they are hesitant to do so, because in their product testing it seems that they only use like 5 or 6 displays.

 

[-Fran-]

https://www.prepar3d.com/SDKv4/prepar3d/views/multimonitor_overview.html

You did read that, I would assume?

Cheers!

 

[FrequentFlyer]

https://www.prepar3d.com/SDKv4/prepar3d/views/multimonitor_overview.html

You did read that, I would assume?

Cheers!

Yep, we did their multichannel setup. Not a fan of it but it works.

 

[FrequentFlyer]

You'll need to contact Lockheed Martin and see if they support such setups directly.

But you are simply expecting too much. Even the best/fastest cards today have problems rendering 4K @ 60fps. The fact you are trying to render to more than 1 is nothing short of insane. Whomever set this system up didn't know what they were doing.

Well, there is only 1 4k display. The rest are either 1920*1080 or close to it. However, I have done tests without using the 4k monitor and there are still issues. I think it does boil down to the 1st graphics card somehow being used for all of the displays. Because I just did another test and reaffirmed that if I only use a single monitor display per graphics card, turn the others on that GPU off, then open up the game, the framerate still drops.

Lastly, I know there are GPUs out there that can do what I need it to do. Theoretically, why wouldn't 4 quadro gv 1000s just magically fix my problem?

 

[-Fran-]

Well, there is only 1 4k display. The rest are either 1920*1080 or close to it. However, I have done tests without using the 4k monitor and there are still issues. I think it does boil down to the 1st graphics card somehow being used for all of the displays. Because I just did another test and reaffirmed that if I only use a single monitor display per graphics card, turn the others on that GPU off, then open up the game, the framerate still drops.

Lastly, I know there are GPUs out there that can do what I need it to do. Theoretically, why wouldn't 4 quadro gv 1000s just magically fix my problem?

It depends on driver support. If you can make the cards work in SLI (or the pro-equivalent from nVidia; which I don't know if it exists) for the Quadro card, then you may be right.

Cheers!

 

[InvalidError]

And like I said, that is defined by what Intel considers their iGPU can handle because of processing capabilities, drivers or lazyness of specs (most businesses just make do with 3 screens tops before using discrete GPUs).

The display limit on Intel's IGP isn't "what Intel considers the IGP can handle", it is simply the number of physical outputs the IGP hardware actually has in it. The IGP has three sets of display output drivers (IO pins) so the IGP physically cannot support any more than three simultaneous independent outputs. Adding extra outputs to the IGP to handle larger multi-monitor setups would be trivial if there was a sufficiently large market to justify it, only need to add pins and DMA engines up to whatever spare memory bandwidth can bear.

 

[-Fran-]

The display limit on Intel's IGP isn't "what Intel considers the IGP can handle", it is simply the number of physical outputs the IGP hardware actually has in it. The IGP has three sets of display output drivers (IO pins) so the IGP physically cannot support any more than three simultaneous independent outputs. Adding extra outputs to the IGP to handle larger multi-monitor setups would be trivial if there was a sufficiently large market to justify it, only need to add pins and DMA engines up to whatever spare memory bandwidth can bear.

You're oh so wrong there. DP split is not always supported with Intel iGPUs, even if they actually come with a DP; hell, they even don't support DVI split in some motherboards, just DVI-I. The GPU itself can't drive more than 2 displays reliably without clocking to max speeds. I have my work laptop with me and I can attest to that end.

Cheers!

 

[InvalidError]

You're oh so wrong there. DP split is not always supported with Intel iGPUs, even if they actually come with a DP; hell, they even don't support DVI split in some motherboards, just DVI-I. The GPU itself can't drive more than 2 displays reliably without clocking to max speeds. I have my work laptop with me and I can attest to that end.

The CPUs themselves have supported three displays for quite a while, though the third port is reserved for eDP which is only useful for AiOs. As for the lack of DP output on boards, that is the board manufacturer and the buyer's problem, not Intel's.

From a purely numerical standpoint, I see no reason why any semi-modern IGP would struggle with driving 2-3 4k60 outputs: each 4k60 requires about 1.5GB/s of memory bandwidth and even good old dual-channel DDR3-1600 can handle close to 25GB/s. If your laptop is struggling to 'reliably' manage two displays, something must be wrong with it. On my GTX1050, refreshing my 4k60+1200p60 setup puts less than a 3% load (~3.2GB/s) on the memory controller including the bandwidth needed to update opened windows that have changes in them and 0-6% load on the GPU core for drawing those changes, should be within the grasp of ~10X slower IGPs.

 

[-Fran-]

The CPUs themselves have supported three displays for quite a while, though the third port is reserved for eDP which is only useful for AiOs. As for the lack of DP output on boards, that is the board manufacturer and the buyer's problem, not Intel's.

From a purely numerical standpoint, I see no reason why any semi-modern IGP would struggle with driving 2-3 4k60 outputs: each 4k60 requires about 1.5GB/s of memory bandwidth and even good old dual-channel DDR3-1600 can handle close to 25GB/s. If your laptop is struggling to 'reliably' manage two displays, something must be wrong with it. On my GTX1050, refreshing my 4k60+1200p60 setup puts less than a 3% load (~3.2GB/s) on the memory controller including the bandwidth needed to update opened windows that have changes in them and 0-6% load on the GPU core for drawing those changes, should be within the grasp of ~10X slower IGPs.

And again, I'm talking from experience.

We have Intel laptops in the Company and even when you have the docking station with enough outputs, the iGPU doesn't support more than 3 simultaneous displays for whatever reason. I have a coworker with an i7 HQ laptop (crazy expensive piece of hardware for the Company) and whenever he opens the lid of the laptop, one of the displays (he has 3 connected via DP and HDMI with an external docking station) always turns off. He's tried researching how to make it display, but the Intel drivers won't allow him.

I don't know what else to tell you 🤷‍♂️

Cheers!

 

[InvalidError]

We have Intel laptops in the Company and even when you have the docking station with enough outputs, the iGPU doesn't support more than 3 simultaneous displays for whatever reason.

OF COURSE it doesn't, the Intel spec is THREE maximum. You need one DMA engine per display that needs to be refreshed since each display gets its own frame buffer and needs to be streamed at a rate that matches each individual display. If you have two displays on DP/MST, then DP consumes two DMA engines out of the IGP's three, leaving you with only one more to either use for the laptop's internal display, HDMI/DVI or a third DP stream.

If you want to have more displays, then you need something like Matrox's Dual/TripleHead-to-Go adapter which takes two or three displays and make them look like one larger monitor to the host PC.