Questions involving old CPU limits

[Kageseigi]

I have an old i7-4820k with an RX 580. I saw that there is a sale on the RX 6600 currently, so I wanted to see how hard DCS was pushing both the CPU and GPU, and if the RX 6600 would be worth upgrading to with my current CPU.

So I managed to get MSI Afterburner working (at least, it seems to be working). I was expecting to see my CPU maxed out, but it actually displayed my GPU as being maxed out, and my CPU didn't even really hit 40% usage.

So I was looking at some YouTube videos to see how well older CPUs could perform on DCS. And I was noticed something. It seems that CPU loads can be nowhere near 100% with the GPU usage pretty low also, but the FPS can be horrendous. For example, in this video...

 

Notice on the left, even though the CPU usage did spike up way high at a few points in this segment, there were times when it was still ~50% with the GPU running under 15%. Yet the FPS was under 15. So I'm curious why neither the GPU or CPU maxed out in order to reach a higher FPS. Or is the display just not accurate? And if that's not the case, then what really was the limiting factor?

And I suppose I may as well ask, in my case, what GPU would max out an i7-4820k? Would an RX 6600 be overkill for it? Though even if so, it may be a decent GPU for when I am able to build a new computer.

Thank you!

[LucShep]

On 4/24/2023 at 4:04 AM, Kageseigi said:

So I was looking at some YouTube videos to see how well older CPUs could perform on DCS. And I was noticed something. It seems that CPU loads can be nowhere near 100% with the GPU usage pretty low also, but the FPS can be horrendous. For example, in this video...

Notice on the left, even though the CPU usage did spike up way high at a few points in this segment, there were times when it was still ~50% with the GPU running under 15%. Yet the FPS was under 15. So I'm curious why neither the GPU or CPU maxed out in order to reach a higher FPS. Or is the display just not accurate? And if that's not the case, then what really was the limiting factor?

Let's separate thing first.

1) DCS World, even with the latest MT introduction, is not using all cores/threads that most CPUs have today. In this initial stage, it only uses the equivalent of 3 to 5 cores/threads in total, at most (with 1 core/thread fully used and alternating work between other cores/threads), at least from what I've noticed.
It'll eventually get to use more with its development, for sure.

So, at this point, you still need a CPU that has really strong single core performance (the so called IPC, "Instructions Per Clock", the potency of each core alone).
The i7-4820K is not "really bad" by any means, but it is vastly outdated - even budget CPUs have surpassed it in this aspect.

The fact that you see just 40% of CPU utilization is partially explained, and it doesn't mean that it's not working as fast as it can.
What it does mean is, that the game can not extract more performance from that CPU, within all of those ~40% of usage that it can take from it.

If you put, say, an i5 13600KF, and run DCS (same mission and all) the CPU utilization will not grow but, with the much higher IPC, its "punch" will be vastly bigger, making quick work of what yours may struggle with, and frames will go much higher. This will also allow the GPU to work more freely (as it too always depends on what the CPU is doing), which also explains what happens in that scenario example.
 

2)  DCS World is, yes, far from being well optimized. But one thing that people often forget is that it uses a lot of scripts and real time calculations (avionics, physics, weapons systems, AI, aerodynamics, weather, etc, etc), a lot of really huge textures, a lot of ultra detailed 3D models, a lot of Shader effects, and huge terrains with all of those running and happening all at same time. On top of that, also many big sound files triggered all at once. 

Sometimes cutting back some detail would be better, and optimizations would be very welcome (and are required).
But the unescapable fact is this - a lot is happening at same time, far beyond (way, waaay beyond) any other "normal" PC game. And that will never change for what this sim/game aims to achieve.

All of that demands a lot and takes it toll, not just in CPU and GPU, but also on RAM and SSD data swap, these too need to do it fast - speed, bandwidth, latencies and caches all play a role here as well. All need to be as good as possible, so that none component drags the others behind.
Something is the bottleneck at any time, no matter how good a PC can be. And, well, sometimes I think not even a NASA computer would be enough (for example, think very busy missions in populated online servers).... 
 

On 4/24/2023 at 4:04 AM, Kageseigi said:

And I suppose I may as well ask, in my case, what GPU would max out an i7-4820k? Would an RX 6600 be overkill for it? Though even if so, it may be a decent GPU for when I am able to build a new computer.

Thank you!

RX6600 is not overkill for the i7 4820K. The truth is, that GPU is also not that great for DCS (good for 1080P resolution with dialed in settings, but not much more).
I wouldn't recommend it, you'd be much better instead with an Nvidia RTX3060Ti or AMD RX6700XT (at most, with that system).

That said, I wouldn't invest any further on that system. 
If DCS is a large part of your free time and you consider flight-simming as a hobby, maybe it's time to think about a total system upgrade.  

Edited April 25, 2023 by LucShep

[BitMaster]

You should also consider RAM bandwidth with that setup as it is DDR3 based. DCS does not utilize all cores equally and thus you will likely never see a CPU at 100% in DCS and if that was the case it would be a major problem whereas a GPU at 100% is what you want, always.

Likely there is 1 core being fully used most of the time, which equals 12.5% of your CPU's 100% ( 8 threads ), there are more threads now with MultiThreading in DCS but they usually do  not saturate the cores like the 1 main thread that drives the sim. So you will likely see 1 core usually maxed out and a few others between 20-80%, kind of like that.

That CPU is too weak per core to justify an investment imho. It's a great home-server thing but too slow for DCS imho.

 

edit.... 

Luc

yeah,  beat me with 3 minutes   haha

Edited April 24, 2023 by BitMaster

[Kageseigi]

Thanks, guys. Yes, a new system (whether 5800X3D or 7800X3D) is the goal. Was just curious if $200 could buy me some time before I have to go $1,000+