Higher resolution monitor affects CPU load or just GPU?

[Naman Malik]

If you make a shift to a higher resolution display then will it affect your CPU performance too or it's just GPU which has to work more due to higher number of pixels

[SupaKomputa]

If not gaming neither will be effected.

For gaming it would be the gpu that stress the most.

[KarathKasun]

FPS goes down, GPU load goes up, CPU load goes down.

[191x7]

In most games, when you increase the resolution, the CPU has to work roughly the same but the GPU load increases.

[KarathKasun]

Just now, 191x7 said:

In most games, when you increase the resolution, the CPU has to work roughly the same but the GPU load increases.

Whenever the FPS goes down CPU load goes down.  Pixels determine GPU load, raw FPS is a indicator of CPU load.

[191x7]

1 hour ago, KarathKasun said:

Whenever the FPS goes down CPU load goes down.  Pixels determine GPU load, raw FPS is a indicator of CPU load.

Not quite. I think you should freshen up your knowledge about the CPU-GPU relationship.

A CPU prepares the frames for the GPU. CPU calculates the relationships, physics etc - and that does not change with the resolution.

[SupaKomputa]

9 hours ago, KarathKasun said:

Whenever the FPS goes down CPU load goes down.  Pixels determine GPU load, raw FPS is a indicator of CPU load.

how do you make this assumption?

[Naman Malik]

Ohk.. so if I have to compare two CPUs (with same GPUs) should I do that at lowest resolution so that the CPUs are not bottlenecked by the GPU 

[KarathKasun]

23 hours ago, 191x7 said:

Not quite. I think you should freshen up your knowledge about the CPU-GPU relationship.

A CPU prepares the frames for the GPU. CPU calculates the relationships, physics etc - and that does not change with the resolution.

You increase resolution, GPU cant draw as many frames in a second, load is lightened on the CPU because it has to calculate updates for fewer frames in the same amount of time.

 

You decrease resolution, GPU draws more frames in a second, load is increased on the CPU because it has to calculate updates for more frames in the same amount of time.

 

How is this difficult to understand?

[KarathKasun]

15 hours ago, Naman Malik said:

Ohk.. so if I have to compare two CPUs (with same GPUs) should I do that at lowest resolution so that the CPUs are not bottlenecked by the GPU 

CPUs should be compared for game performance at the lowest resolution.  However, this is not a good indicator of future performance.  It is only a "ok" indicator of how fast the CPU can run the same game with a faster GPU whenever that becomes available.

[191x7]

3 minutes ago, KarathKasun said:

You increase resolution, GPU cant draw as many frames in a second, load is lightened on the CPU because it has to calculate updates for fewer frames in the same amount of time.

 

You decrease resolution, GPU draws more frames in a second, load is increased on the CPU because it has to calculate updates for more frames in the same amount of time.

 

How is this difficult to understand?

The thing is - the CPU does not wait for information from the GPU - it prepares as many frames as it can (this might be limited by the software, the game engine etc) and forwards those to the GPU (*draw calls*). If the GPU can do more, it's bottlenecked, if the GPU can't do all of them it's simply used 100% and not all CPU prepared frames are rendered.

[KarathKasun]

3 minutes ago, 191x7 said:

The thing is - the CPU does not wait for information from the GPU - it prepares as many frames as it can (this might be limited by the software, the game engine etc) and forwards those to the GPU (*draw calls*). If the GPU can do more, it's bottlenecked, if the GPU can't do all of them it's simply used 100% and not all CPU prepared frames are rendered.

False.  The CPU waits for the GPU to become ready before dispatching more draw calls.

 

I can set arbitrary FPS limits and watch CPU load increase or decrease.  What you are saying is not how things work.

[191x7]

KarathKasun, are you actually telling us a GPU can bottleneck a CPU?

[KarathKasun]

Just now, 191x7 said:

KarathKasun, are you actually telling us a GPU can bottleneck a CPU?

YES

[KarathKasun]

You are aiming to have the GPU be your only bottleneck in gaming systems.

[191x7]

Well, that is false, at least for most game engines.

[KarathKasun]

1 minute ago, 191x7 said:

Well, that is false, at least for most game engines.

No, no its not.

 

Use DSR/VSR to scale up to 4k and pay attention to CPU load.

[JoostinOnline]

1 hour ago, 191x7 said:

KarathKasun, are you actually telling us a GPU can bottleneck a CPU?

It absolutely can. Try comparing your CPU load on a modern game when running integrated graphics vs discrete graphics. It's why CPU tests are usually run with the highest end GPU that can be afforded and with the resolution turned to something lower.

[KarathKasun]

Just threw a pretty CPU intensive game (Battletech, ST intensive) at my ancient rig (2600k @ 4.4ghz + RX 560 4gb).  CPU load is as follows...

720p ~30%

1080p ~20%

2160p ~10%.

[Naman Malik]

If both CPU and GPU can be bottlenecked by each other so is it theoretically nearly impossible to have a system without bottlenecks??

[KarathKasun]

Just now, Naman Malik said:

If both CPU and GPU can be bottlenecked by each other so is it theoretically nearly impossible to have a system without bottlenecks??

Correct.  You want a CPU fast enough to not limit your GPU,  so your GPU performance is your limiting factor.

 

If you do game streaming or recording, you will need more CPU power for the same performance.  Same goes for those who multitask, tons of browser tabs open while gaming for example.

[KarathKasun]

Another way of thinking about it is...

 

If you had zero bottlenecks you would have infinite FPS, which is impossible.

[191x7]

This is some interesting read. I'm wondering on how a CPU can prepare more frames than a GPU can render. For example, in Battlefield V one can have a CPU bottleneck when the average frametime of the CPU is 16.6 ms and the average GPU frametime is 10ms, but it can go the other way around - you can have a CPU frametime of 10 and a GPU of 16.  If the CPU had to wait on the GPU, I don't think we'd have such a difference in frametimes.

The thought that it might be engine related never crossed my mind, I believed it to be so in all the games.

[GeoSquigg]

22 hours ago, SupaKomputa said:

how do you make this assumption?

Just messing around with my 2200g and cities skylines:

 

1440p= CPU 40% - APU 100%

1080p= CPU 55% - APU 100%

720p= Cpu 70% - APU 100%

[KarathKasun]

5 hours ago, 191x7 said:

This is some interesting read. I'm wondering on how a CPU can prepare more frames than a GPU can render. For example, in Battlefield V one can have a CPU bottleneck when the average frametime of the CPU is 16.6 ms and the average GPU frametime is 10ms, but it can go the other way around - you can have a CPU frametime of 10 and a GPU of 16.  If the CPU had to wait on the GPU, I don't think we'd have such a difference in frametimes.

The thought that it might be engine related never crossed my mind, I believed it to be so in all the games.

What you may be looking at is the Physics FPS, which is not the same as per frame CPU overhead.