OS X Tomb Raider on cMP & GTX1080: extreme lags in huge areas though great fps in benchmark

[Canubis]

I am playing Tomb Raider (2013) on my classic Mac Pro 4,1 (2009), which got an NVIDIA GTX 1080 GPU upgrade a year ago.
I have 36GB of RAM, mac OS 10.13.6 and the game are running on a 2TB Crucial SSD (600GB free space).

In smaller areas everything feels super smooth & the built-in benchmark shows 100fps avg. with all graphics options set to max and resolution set to 2560x1600.

But in larger areas like Shantytown (esp. when looking into direction of the bridge) or in very action rich sequences, cutscenes etc. I can feel a dramatic lag, basically making the game unplayable. The interesting part is, it seems to be unrelated to any graphics settings. Even if I set everything to the lowest values, there still are basically the same lags in these areas.

Sure, this Mac is far from latest tech. On the other hand this game also is 6+ years old by now and the GTX1080 should handle it perfectly well.

Could the ageing Xeon CPU, which was the entry-level Octo core 2.26GHz config back in 2009, be the actual bottleneck here?
Or some other component?
Would a CPU upgrade to 12-core 3.46GHz possibly solve these issues? (Not planning to retire this Mac soon and upgrading these CPUs seems to be inexpensive these days.)


Any other Tomb Raider players here with similar setup & same (or different?) experience?


While playing in Shantytown level with some extreme lags, I briefly switched to Activity Monitor to check CPU & GPU showing this – note the GPU seems to be bored but also none of the CPU cores is really maxed out:

While using the built-in benchmark with some 100fps avg. framerate (see below) the GTX1080 seems to be much more busy, on the CPU things look similar to above:

 

[Plutonius]

It could be the game coding itself.

Are you able to reduce viewing distance ?

 

[Canubis]

@Plutonius, There are no options for anything like that unfortunately.

 

[Canubis]

Generally thinking – please tell me if there is a mistake:
Unless some limiter like VSYNC is on (which I turned off), the goal of a GPU would be to produce as many frames per second as possible. Therefore ideally the GPU should show close to 100% usage in activity monitor.
If this doesn't happen, some other component must be the bottleneck, right?
The next best idea coming to my mind would be the CPU as bottleneck, which basically needs to tell the GPU what to render. Right? Could any other component be the bottleneck?

 

[Ritsuka]

The CPU, and macOS OpenGL implementation. And probably the way the game engine works. On my MacBook Pro + eGPU Shadow of The Tomb Raider runs better than the 2013 one.