CPU Bound in AC

[EIF]

I have just bought a 144Hz 1080p monitor and have great, very smooth performance alone in a practice session. 120 to 141 fps and max gpu usage.

However In a race against AI my fps drops to 60-100 and gpu usage is only between 50-70%. Even with gsync enabled it still looks choppy as well. In Render stats the Main_T is begged at around 95%, actual cpu usage is less though at around 65-85

I believe this has always been an issue with AC but until now I played at 60Hz vsynced so it wasn't as noticable, but pushing high fps at a relatively low resolution is making things even worse now. Other sims like AMS2 are gpu bound on my system but I still get nice high framerates above 100 and against AI, races actually feel smoother than in AC.

I'm using a 9 year old system, i5 2500K 8GB DDR3 GTX1060 6GB with AC installed on a Samsung 850 SSD. Does anyone have experience with AC on more modern cpu platforms like Ryzen or latest Intel? I've read about users with 8700K or Ryzen 3600X having the exact same issues so I'm concerned about spending on hardware upgrades that will not show much improvement. Sim racing is all I care about gaming wise these days with AC still my main sim after 7 years, so looking for a upgrade that will benefit it.

Any advice on settings to improve things? Ive tried running AC vanilla without cm/csp/sol etc or even additional apps without luck.

 

[Stereo]

MAIN_T is single-thread performance, as far as I know it's proportional to number of cars you have for a couple reasons (collisions, graphics stuff, audio) that are just using libraries (fmod, directx) that don't multithread and that's why it tends to max out first. It limits framerate through the directx component of that.

A faster cpu should help MAIN_T, I don't know if it'll actually improve framerate.

 

[aphidgod]

FWIW i found more frames on my old i7-3700k/GTX670 setup by clocking the CPU higher than I did by doing the GPU. There are gains to be found IMO but I couldn't say how much.

 

[EIF]

I have my i5 overclocked by adjusting the multiplier because I don't want the pc running at max clock and volts all the time. Its only at 4.2Ghz, any higher will bsod, got a poor overclocker.

Adjusting graphical settings really doesn't do much because I am cpu bound so the only solution so far is to reduce the amount of AI, which reduces the enjoyment.

I'm looking to upgrade my system since its so old anyway, but I'm worried something like a high core count Ryzen 5000 cpu wouldn't actually help much because AC is so dependant on single core performance. Would Intel be a better choice? What cpus are people using in AC these days?

 

[bondyboy]

I have my i5 overclocked by adjusting the multiplier because I don't want the pc running at max clock and volts all the time. Its only at 4.2Ghz, any higher will bsod, got a poor overclocker.

Adjusting graphical settings really doesn't do much because I am cpu bound so the only solution so far is to reduce the amount of AI, which reduces the enjoyment.

I'm looking to upgrade my system since its so old anyway, but I'm worried something like a high core count Ryzen 5000 cpu wouldn't actually help much because AC is so dependant on single core performance. Would Intel be a better choice? What cpus are people using in AC these days?

Wow 4.2 is quite low for that chip, mine was running a constant 4.8 for about 5 years - what motherboard and cpu cooler have you got?

 

[McGherkin]

Can’t copy/paste from Reddit on my phone but this is from AC’s devs.

Whilst AC is partially single threaded AI physics should scale.

For what it’s worth, I can blow all threads on my OC’ed 4690k with 20-30 cars.

 

[EIF]

Wow 4.2 is quite low for that chip, mine was running a constant 4.8 for about 5 years - what motherboard and cpu cooler have you got?

Mobo is a MSI P67a-GD65, cooler is an old Corsair A50 Aircooler. I'm sure if I manually adjusted the vcore it would go higher, will give it a try since I have nothing to lose with the cpu giving 9 years of great service.

I just set the multiplyer to 42 (43 would bsod even in Firefox) because I'm not a confident overclocker and didn't want max vcore the whole time because the system can be on for long hours.

Apart from the choppyness at high framerate, I sometimes get slow-motion play despite good framerates. Using the new Suzuka ACC conversion for example, running more than 15 AI causes super slo-motion at the start of a race, though 99% of my other tracks dont have this issue.

 

[RasmusP]

Mobo is a MSI P67a-GD65, cooler is an old Corsair A50 Aircooler. I'm sure if I manually adjusted the vcore it would go higher, will give it a try since I have nothing to lose with the cpu giving 9 years of great service.

I just set the multiplyer to 42 (43 would bsod even in Firefox) because I'm not a confident overclocker and didn't want max vcore the whole time because the system can be on for long hours.

Apart from the choppyness at high framerate, I sometimes get slow-motion play despite good framerates. Using the new Suzuka ACC conversion for example, running more than 15 AI causes super slo-motion at the start of a race, though 99% of my other tracks dont have this issue.

Not wanting to re-activate the thread but just wanna drop the info for other people finding this thread with similar issues.

Get content manager, install custom shaders patch (csp) and disable everything apart from the custom font rendering and the cpu optimizations in the "general" csp section.

This greatly improves main_t!

The slow motion although having good fps is probably the main_t maxing out and AC getting physics glitches.
We had a few drivers with this problem in the online racing club and when it happened, they were jumping around the track, causing accidents with others.

So we solved it

 

[Ben Lee]

I was surprised to hear that the engine doesn't scale "well" with multiple CPUs as the intial AC trailer said that it had "heavy multithreading"...

I personally have never really had a problem with performance of AC.

https://www.facebook.com/video.php?v=10150690245403069

 

[RasmusP]

I was surprised to hear that the engine doesn't scale "well" with multiple CPUs as the intial AC trailer said that it had "heavy multithreading"...

I personally have never really had a problem with performance of AC.

https://www.facebook.com/video.php?v=10150690245403069

I wouldn't call this "Heavy Multithreading":
More like... "Dual threading"...

(It's with my old 4c/8t i7 2600k. So maximum of a single thread is 100% divided by 8 = 12.5%).
What you can see is one thread probably hitting the limit at 12.39% and another thread almost hitting the limit at 12.31%. And then a few smaller threads... That's a race replay with 30 cars. A live race with AI will show a bit different numbers but not much.

My "problems" with AC's performance started when my fps dropped below 60 after installed "Substanding" for online races. Great leaderboard overlay to keep overview when being the race host but it really killed my fps.
With CSP, the impact of it is reduced massively and I could use it again

 

[EIF]

How does AC perform with the latest Ryzen like the 5600X? Its time I ditch the old 2500K, my GTX 1060 will have to do a while longer though

 

[RasmusP]

How does AC perform with the latest Ryzen like the 5600X? Its time I ditch the old 2500K, my GTX 1060 will have to do a while longer though

Absolutely awesomely great!
I went from 2600k OC'ed to 4.4 GHz to 10600k at 4.9 GHz. I would have loved to get a 5600x but couldn't wait another year...

When you do a Cinebench R15 run with 3 and with 4 threads, you'll come pretty close to how AC performs.
I gathered quite some info from people I talked to about this topic. I'll spare you the points etc and just show you the summary plot normalized to MY 10600k theoretically achieving 90 fps.
(I simply took the CB 15 results, took the % difference to my cpu and set my cpu to be "90". )

 

[EIF]

Nice numbers. My concern was how much an older sim like AC would benefit from the latest multi core/threads cpus. AC is still my go-to-sim and it still runs ok on my old system but I think a new cpu would make it a much smoother experience at high framerates/low resolution.

 

[dwightyone]

Yeah I have 5600x combined with rtx3070 on one of my two rigs and with one GT3 car on the track the main t is less than 9% whereas the same car and track on my 6700k/rtx 2070 super is around 16-17% main t

 

[EIF]

How is it with large grids of AI?

 

[RasmusP]

Nice numbers. My concern was how much an older sim like AC would benefit from the latest multi core/threads cpus. AC is still my go-to-sim and it still runs ok on my old system but I think a new cpu would make it a much smoother experience at high framerates/low resolution.

For ac you don't really gain anything with more than 4 cores. But with really just 4 cores without ht/smt, you can get spikes close to full cpu load.
So 4c/8t or 5 physical cores are the minimum for best performance.
After that, only the single core performance is important.

But there are no 4c/8t CPUs with comparable single core performance on the market and also no 6c CPUs without virtual doubling so the 5600x really is the best choice.

The 5800x or 5900x won't really give you more fps. They just clock a bit higher and have a bigger cache, which gives a few fps on top but in absolutely no relation to the costs...

 

[EIF]

Thanks for the information I only run 1080p at 144Hz so my GTX 1060 can cope a while longer (I don't have a choice given the shortage ha) but seems a 5600x would make a nice upgrade.

 

[dwightyone]

How is it with large grids of AI?

Haven't checked off hand - to busy sorting my mod collection out rather than actually racing. I'll check later and will post back but am expecting goodness

 

[EIF]

Haven't checked off hand - to busy sorting my mod collection out rather than actually racing.

Ha I know that feeling!

 

[Lizard Of Bodom]

Thanks for the information I only run 1080p at 144Hz so my GTX 1060 can cope a while longer (I don't have a choice given the shortage ha) but seems a 5600x would make a nice upgrade.

if I may help out your question - I did direct swap from 3750k with 980SLI to 3700X with the same 980SLI setup (with change of mobo and DDR4 ofcourse) and I have to say difference was collossal. I was getting constant "CPU max usage" errros on heavy multiplayer tracks like LAC, was gettng more stuttering and lower FPS in general. Have no problems with CPU since change, it oscillates in 20-25% usage and now the only bottleneck is GPU setup.
I also play 99% in AC, built whole system around it, but changing CPU will benefit more than changing GPU in your case (IMO).