GPU working w/o cable??!!

[shaheerbhai001]

i went to a friends house to play some games and i noticed that his HDMI cable was plugged into his motherboard. I told his that it had to be in the GPU but he said that everything was working fine. I tested and it was indeed working fine. BUT heres the kicker when i removed the cable from the motherboard and plugged it into the gpu THE PERFORMANCE DROPPED!! like by 5-10%!!!

now to do some testing i tried diasbling the GPU, after that when i ran the game, it ran horribly, which is understandable. BUT what i dont understand is how was the gpu impacting the performance when it wasnt even plugged into the monitor. can gpus now just do that? am i getting too old? 

another thing, the monitor was also showing that the signal was coming from the iGPU alone.

 

Here are my questions:

1. How does a GPU impact performance when there is no cable coming out of it. (The GPU was being used, like i could see the GPU usage in afterburner and also noticed the temprature rise)

2. Why did the performance drop when i plugged the cable into the GPU instead of the motherboard.

Specs:

Ryzen 7 7700

Asus TUF B650-M wifi

Zotac 5070

[Eigenvektor]

19 minutes ago, shaheerbhai001 said:

1. How does a GPU impact performance when there is no cable coming out of it. (The GPU was being used, like i could see the GPU usage in afterburner and also noticed the temprature rise)

Interesting. That's something I would normally only expect from a laptop, where the discrete GPU's output is often routed through the iGPU. Not something you normally see on a desktop.

 

19 minutes ago, shaheerbhai001 said:

2. Why did the performance drop when i plugged the cable into the GPU instead of the motherboard.

Did you reboot the system in between and run the test multiple times? Otherwise this could be an effect caused by something else running in the background, that just happened at the right time to impact the results.

 

I don't see how this could improve performance, unless some of the GPU's workload got offloaded to the iGPU somehow. Only thing that comes to mind would be something like Lossless Scaling. That might also explain why it's output was visible through the iGPU.

[y0ur5h4d0w]

50 minutes ago, shaheerbhai001 said:

1. How does a GPU impact performance when there is no cable coming out of it. (The GPU was being used, like i could see the GPU usage in afterburner and also noticed the temprature rise)

using the nvidia control panel you can control which application uses the GPU or the integrated graphics by forcing one of the options. and i belive that there's a control inside windows settings too which allows you to select which GPU to use, should be set to "auto" by default and based of the type of application windows knows if has to redirect data through the iGPU or the GPU

 

 

50 minutes ago, shaheerbhai001 said:

2. Why did the performance drop when i plugged the cable into the GPU instead of the motherboard.

well you first have your iGPU (integrated GPU) having to do the "screen handling" and then you have your actual GPU to handle even the screen and all the other applications, but i doubt that the performances drop would be actually that noticeable, unless you have a big monitor

[thekingofmonks]

2 hours ago, shaheerbhai001 said:

when i removed the cable from the motherboard and plugged it into the gpu THE PERFORMANCE DROPPED!! like by 5-10%

What did you test performance with?

 

2 hours ago, Eigenvektor said:

Interesting. That's something I would normally only expect from a laptop, where the discrete GPU's output is often routed through the iGPU. Not something you normally see on a desktop.

Nvidia Optimus can be configured on desktops, I imagine it's the same with AMD

[GuiltySpark_]

I think what's abundantly clear here is there is a missing detail that is being overlooked. You're simply not going to improve performance by routing through the system and out the iGPU. 

 

14 minutes ago, thekingofmonks said:

Nvidia Optimus can be configured on desktops, I imagine it's the same with AMD

I've never seen Optimus as a configurable option in the NVCP or NVApp on desktops with iGPU's. Are you just referring to Windows ability to pick a render GPU in Settings > Display > Graphics? 

[Eigenvektor]

27 minutes ago, thekingofmonks said:

Nvidia Optimus can be configured on desktops, I imagine it's the same with AMD

Didn't know that was a thing on desktop. Thought that requires the discrete GPU's output to be routed through the iGPU, though I guess technically that could be done through the PCIe bus.

[shaheerbhai001]

@Eigenvektor the thing is, i dont think it was running on the igpu at all. I was running Forza Horizon 5 at max high settings with dlss and was getting 200+ fps.

 

[shaheerbhai001]

@y0ur5h4d0w just as lost as you are

 

[shaheerbhai001]

@thekingofmonksForza 5 with ray tracing. i was getting 210 ish fps but after connecting the hdmi to the gpu it went down to 180

 

[Eigenvektor]

2 hours ago, shaheerbhai001 said:

@Eigenvektor the thing is, i dont think it was running on the igpu at all. I was running Forza Horizon 5 at max high settings with dlss and was getting 200+ fps.

Yeah. What I mean is, it sounds like it was running on the GPU, but its output was getting routed through the iGPU. Because the monitor ports on the motherboard are only connected to the iGPU (as you probably know)

 

The only thing I can think of that could potentially explain a performance difference after switching is something like upscaling running on the iGPU. E.g. using something like LS to run the game on one GPU, while using the other purely for upscaling.

 

But I think the more likely cause is a measuring error. Something running in the background affecting the outcome. So I'd repeat the test for each configuration multiple times and possibly reboot after switching ports, to rule out weird side effects. If you take the average of three runs and it's still a 5-10% difference, then I believe something is going on. Otherwise, it's likely just a fluke.

[y0ur5h4d0w]

3 hours ago, shaheerbhai001 said:

@y0ur5h4d0w just as lost as you are

 

i try to re-explain myself:

 

so you have the GPU and the iGPU, in the case of the "GPU working without a cable" it's indeed a way to run theGPU. What happens essentially is that your monitors are controller by your CPU (the iGPU is the graphic part of your CPU) but all the data is processed by your GPU, this means that the data traffic is redirected first to your GPU which calculates the data then it's transported to the iGPU that displays directly on the screen what have been processed. 

 

this process CAN have benefits since some GPU strength can be sucked up by the the fact that your GPU display image directly on your monitor and this takes a part of compute power, so, if you experience better FPS when you have your cable plugged directly into your motherboard while having a GPU is totally normal. 

 

if i remember correctly there was a video from linus where he was explaining that "the second monitor is killing your GPU performances" or something similiar which should talk about something that might help you understand the reason why running the iGPU for the monitor is beneficial even if it's minimum:
 

[shaheerbhai001]

12 hours ago, Eigenvektor said:

Yeah. What I mean is, it sounds like it was running on the GPU, but its output was getting routed through the iGPU. Because the monitor ports on the motherboard are only connected to the iGPU (as you probably know)

WHAT!? GPUs can do that? I thought they only affected performance when the output is coming directly off of the actual card.

[Eigenvektor]

4 minutes ago, shaheerbhai001 said:

WHAT!? GPUs can do that? I thought they only affected performance when the output is coming directly off of the actual card.

What part exactly are you referring to?

 

A GPU's display out getting routed through the iGPU for connecting an (external) monitor is commonplace in laptops. Though sometimes one of a laptop's monitor ports may be directly connected to the discrete GPU. I wasn't aware this is something that could work out of the box on desktops. But as was said above, supposedly Nvidia Optimus makes it possible?

 

Since there's no dedicated physical connection between the GPU and iGPU, that would require output to be transported over the PCIe bus. Basically: GPU renders image, image is sent over PCIe to the iGPU, iGPU sends image to monitor. But if anything, I would expect that to decrease performance, not increase it.

 

As I said, I could imagine an increase if and only if the GPU renders the image at a lower resolution, sends it to the iGPU and the iGPU then does the upscaling. Splitting work this way might potentially increase performance. At the expense of latency introduced by sending data over PCIe.

 

Is that what's going on? I have no idea. Just thinking of possible technical explanations. But again, I'd perform multiple benchmark runs first, to rule out that the apparent performance increase (or decrease) was caused by some other factor entirely.

[NanoBleed]

It's normal. When you plug into the motherboard, the iGPU just acts as a passthrough, and the 5070 still does the rendering. Directly plugging into the GPU adds output load, so you might see a small FPS drop. You can disable the iGPU in BIOS and test.