CPU usage vs Main_t value

[Crispin Williamson]

Hi,

I'm playing around with my PC altering graphics settings and played with overclocking to see if it made much difference, it didnt. When playing with a full grid my Main_t value gets near 100% and I get frame rate drop, when I have MSI running however it shows that my CPU (all 4 cores) are nowhere near maxed out, my graphics card (980ti) is plodding along.

Am I missing something here?

Cheers

 

[StefanoCasillo]

Am I missing something here?

yes, the meaning of the value (MAIN_T) in AC.
The number shows the relationship between the time spent inside the game code in a frame and the total time of a frame.
No relationship whatsoever with a CPU occupancy value, and it was renamed just with the hope that people will stop treating it as a CPU occupancy indicator and getting confused about it.

 

[Crispin Williamson]

yes, the meaning of the value (MAIN_T) in AC.
The number shows the relationship between the time spent inside the game code in a frame and the total time of a frame.
No relationship whatsoever with a CPU occupancy value, and it was renamed just with the hope that people will stop treating it as a CPU occupancy indicator and getting confused about it.

Thank you, so my performance is limited by this factor and not my CPU or GPU? Can I do anything to improve performance?

 

[StefanoCasillo]

A high value of main_t suggests the game could be CPU bound... but it could really be other things from RAM speed to BUS speed, PCs are complicated beasts.

 

[Crispin Williamson]

My CPU values are quite low. Anyone got any tips?

 

[KToMmi]

Hi,

I'm playing around with my PC altering graphics settings and played with overclocking to see if it made much difference, it didnt. When playing with a full grid my Main_t value gets near 100% and I get frame rate drop, when I have MSI running however it shows that my CPU (all 4 cores) are nowhere near maxed out, my graphics card (980ti) is plodding along.

Am I missing something here?

Cheers

Hi, did you ever manage to lower your MAIN_T values?
I have been experiencing the same issues for a couple of weeks even though my CPU isn't bad at all (i7-6820HQ) and even though it has always worked perfectly fine. I have not found a freaking solution yet.

 

[dud]

Just because no specific CPU core is maxed out during an observation period that does not mean that there isn't a single-threaded segment holding up the show. A single thread can be freely rescheduled to run on different cores. Looking at that thread in isolation and at that complete process would reveal that there is 100% CPU usage of one CPU during that period, however which specific hardware core provided that execution unit can change during the observation period. But that is hard to observe for verification from the outside, you generally want source code and debugging for this.

 

[RasmusP]

From my experience it's just your CPU.
But as said, it's complicated!

What you can do about it:
Overclock the CPU and/or your RAM. If you can't do that (any higher) you're left with changing settings like:
- disable all apps/hud
- disable the apps you don't need in the main menu
- put reflections to static
- reduce shadow settings
- run fewer AI

If you're running any limiter and not vsync, lower the fps limit to something, you can maintain more consistently.

The root problem is that you just cannot split some things of the program any further after some point so as stated above, there is one thread that loads one core to 100% for a split second you won't see on any CPU load measurement. But it's there!

Hopefully the next generation of Sims will have better multicore support. Or better said, "splitability" of threads.
Funny thing where my knowledge ends is that hyper threading, more cpu cores etc increase the fps although it's a single thread problem.

 

[dud]

As always the best test to see whether you are in any way CPU capped (multithreaded or not) is to downclock the CPU. Downclocking is a lot easier to do (just set the CPU divider lower, which almost all BIOSes allow) than overclocking, and of course safe.

You should disable turbo mode for those experiments, though. So that your downclocked CPU doesn't end up running more turbo, messing up the result.

 

[Fernando Deutsch]

Interesting post.

Here are some samples of screen captures where MAIN_T is high and seems no CPU/GPU is intensive used. RivaTunner stats are GPU temp/%/FB/BUS/MEM.

First view the 3D scenery is complex as it includes main straight and Eau Rouge. Check the value of SCENE and TRI are quiet big.

Another 3D scenery of the straight Eau Rouge/Les Combes. Scene is not that complex but TRI is kind of high due to high LOD cars.

This is your "regular" camera view with no complex 3D scenery

CPU/GPU stats shows they are not really stressed. Same could be said from FB and BUS usage. I am using a 2500K @ 4.2 Ghz, GeForce 1060 3GB. PCIe 16x 2.0.

PD, @kunos please use coma separators on the stat numbers, my eyes hurts trying to read if they are millions,billions,gazillions

 

[Fernando Deutsch]

I know this is kind of old, but I want to share some updates.

At the end of 2018 upgraded to a new i3-8530k from my old i5-2500k. Same number of cores, no HT.
Ensuring using the same CPU speed but with different memory speeds (DDR3 1600 vs DDR4 3200) the new result I got from the La Source apex camera view (the first image) was over 70fps. Playing with memory speeds I could see the thread was limited by the memory access speed rather than CPU or GPU. This situation seems to only happen when there is a heavy 3D scene to be rendered.

 

[Tummie555]

Does anybody know the answer to this:

My Main_t drops with more AI...

Single practice (kunos car, kunos track): 98,3
45 AI on LA Cayons: 93,5

This happens with every combination. The More AI, the lower my Main_T.

(pc: i7 10700k, 16gb 3466mhz, gtx1080ti)

 

[Stereo]

your framerate probably ends up GPU limited with lots of ai so the cpu is spending less time active.

 

[Deleted member 197115]

MAIN_T for whatever reason always shows near 99% in VR usage unless you set FPS limiter. But it has no impact to performance whatsoever.
Either set limiter to 90 fps or use fpsVR.