Understanding CPU vs GPU frame times in BF4

[n0x1ous]

So Im sure most us are familiar with the perfoverlay.drawgraph 1 console command. I understand low is good and 16.6ms = 60 fps etc etc.

What I'm not exactly clear on is the differences between cpu vs gpu frametimes and how they correlate to each other. for example, why is that the cpu frametime drives the framerate. For example the fps display will show 120 and cpu frame time of 8.3 which makes sense, but the gpu frame time will be 14 or 15.....

wouldn't that mean the real framerate is only slightly above 60? shouldnt the fps display match up with GPU frametime?

EDIT:

this only seems to happen in multigpu. If I disable SLI then the cpu and gpu frametimes are in sync and everything makes sense. does this overlay tool show double GPU frametimes if you have 2 cards?

 

[Gloomy]

The GPUs work on more than one frame at a time.

 

[n0x1ous]

The GPU works on more than one frame at a time.

See edit and also explain more....so what is the 14 ms or so telling me in this case then.....and your saying the FPS counter is accurate based off CPU frametime graph then?

 

[Gloomy]

See edit and also explain more....so what is the 14 ms or so telling me in this case then.....and your saying the FPS counter is accurate based off CPU frametime graph then?

You have two GPUs, so it renders two frames at a time, and it adds the time up. That's why you get the higher number for multi-GPU.

 

[UaVaj]

my understanding is that
the cpu frame time is as is.
the gpu frame time is divided by the each gpu.

using your example.
so if cpu frame time is 8ms (aka 125ps)
and
if gpu frame time is 14ms (per gpu), so if for 2 gpu that would be 7ms (aka 142fps)

this would suggest a cpu bottle neck.

 

[BrightCandle]

Its never been made clear what these things are measuring and what the relationship between them is.

 

[Ed1]

I tried that on my system , single 660ti with 3570k and got lower GPU times on avg around 10ms with CPU at 13ms but I have it set in BF4 config to cap fps at 75 , so later I try uncapping and see how close thy match.

CPU line is straight flat line in gameplay with GPU very small variance (2-3ms ) .

Edit;
raised cap to 95 and both lines match up pretty good , did get a crash/freeze with performance overlay , is that buggy ?