GPU vs. CPU Usage in Prepar3d v4.x

WB FlashOver · August 6, 2018

Hello all, I'm new to this forum. After watching Linus' video on bottlenecking I have a few questions. My system usage is primarily for Flight Simming in P3Dv4.3. I have lots of custom scenery installed, 3rd party weather engine, and after market aircraft from A2A Simulations. I run Open Hardware Monitor to keep track of temps and such. I find it very interesting to watch the CPU vs. GPU usage. 'Most' of the time my GPU is at 95%+ load with the CPU at 50-60% load. However, there are times when the CPU is at 90%+ and the GPU is at 50%. They are never running the same, percentage wise. If one is high the other is much lower. I do not believe this to be bottlenecking but I'm not knowledgeable enough to know for sure.

Flight Simming has always proven to be a CPU intensive program but with the advent of Lockheed Martin's P3Dv4.x (64bit program as compared to the 32bit of older sims) which is utilizing more of the GPU it stands to reason that the system should run more balanced.

Really, my questions are,

1) if a system is balanced should not both units be working equally most of the time?

2) why would CPU go down when GPU is up and visa versa?

3) would an upgrade to a 1080 Ti make much of an improvement?

Thanks much

Roger

Motherboard: Asus X99-A
Processor: i7 5930K @ 4625Hz (HT off)
Memory: G-Skill F4-3000C15Q-16GRK
GPU: EVGA GTX 980 Ti 06G-P4-4995-KR 6GB
Sound: Onboard ALC1150
Monitor: Acer XB270HU Abprz Black 27" 144Hz 1ms
Storage #1: Samsung 950 Pro NVMe 256GB
Storage #2: Samsung 850 Evo 500GB x2 Raid0
Cooler: Custom EKWB Cooling Loop (CPU & GPU w/360mm + 140mm rads)
Power Supply: Rosewill Lightning 1300W
OS: Win 10 Pro

Fullmental · August 6, 2018

1) If a system is significantly limited by one or the other, you would have instances where the GPU or CPU is pegged at 100% while the other is barely doing anything for an extended period of time. Even the best processor can hit 100% utilization, and even the best GPU can do the same. Even then, some other component or operation can be at its limit during these operations, such as RAM speed/latency, I/O, or thermal/power limits. you will almost never see the CPU and GPU being utilized at the exact same percentage and shouldn't aim for that.

Your system sounds balanced.

Take a look at this video from LTT that just came out today, it talks about "bottlenecks", how they occur, and why you really shouldn't worry about it so much as long as you're in the ballpark:

2) In FSX/P3D, a lot of the individual objects and aircraft take significant CPU usage in addition to GPU, whereas object complexity and detail can take a toll on GPU.

3) a 1080Ti might improve your FPS, but then again it might not. If you are already seeing a steady 144fps (or whatever refresh rate you game at), then getting a new GPU would do absolutely nothing.The 1080Ti is also not recommended at the moment, as we could see new GPUs out as early as this month and a 980Ti to a 1080Ti is just not that much of a jump when gaming at 1440p/144hz. If you were gaming at 4K, it might make more of a difference.

WB FlashOver · August 6, 2018

Thanks for your reply Fullmental.

1) This was my assessment too so thanks for verifying Sir. Today's video by LTT is what got me to wondering. I do enjoy his videos with loads of information.

2) Make total sense and I agree that different objects require one piece of hardware more over the other. It just seems weird that during a single flight in same aircraft with slightly changing weather the usage would vary so much. "Things that make you go... Hmmmmm". I can always count on 100% GPU usage while sitting in the flight engineers seat. This makes sense as there are many gauges twitching and bouncing with a great amount of attention to detail by the developer.

3) Good information. I have been toying with an upgrade in GPU but waiting makes total sense. I like lots of eye candy so my sliders are set to achieve lots of sweets while maintaining 50-60 FPS.

Many thanks Sir

Roger