How to determine if you're going to have a CPU bottleneck

[Mira Yurizaki]

A concern that comes up a lot in PC gaming circles is whether or not there's going to be a bottleneck somewhere in the system. Unfortunately the answer is, and always will be: it depends. Bottlenecking is not a problem, it's a symptom of one. The problem is that the PC isn't meeting some performance requirement that you want. In related note, having the CPU and GPU at 100% utilization or rather "seeking balance" should not be the end goal. A lower end processor, like an Intel Pentium, is balanced with a lower end GPU, like a GeForce GT 1030, but performance wise it's low-end.

 

Do note for games, there are two primary sources of bottlenecks:

• The GPU: The GPU literally cannot push more frames out. This is more favorable of the two since it's less of a hassle to upgrade the GPU than the CPU (which often when it's necessary requires an entire system upgrade).
• The CPU: The CPU is too busy in some form or fashion to process the game logic and compile work for the GPU to do, limiting frame rate to a maximum that the GPU can easily exceed.

If you want to know more about the interaction between the two in games, I wrote an article about it at:

 

Since the primary bottleneck concern is the CPU one rather than the GPU one, this topic will focus on the CPU bottleneck.

 

Simplified answer tables to "Will I have a bottleneck?"

The following tables provide an answer depending on the relative performance of your CPU, how CPU intensive the game is, and what settings you're playing the game at. This will not say how much of a bottleneck your system will experience as that's highly specific to the game and hardware configuration. So just because the answer is "Yes", doesn't mean your system will be getting a massive hit.

 

These tables are also assuming using a GPU of relatively high performance, like an RTX 2060 Super or an RX 5700.

 

Low single thread performance CPU

	Light CPU usage	High single thread usage	High multithread usage
Res: <= 1080p Settings: <= Med	Yes	Yes	Yes
Res: <= 1080p Settings: >= High	No	Yes	Yes
Res: >= 1440p Settings: <= Med	Yes	Yes	Yes
Res: >= 1440p Settings: >= High	No	Yes	Yes

 

High single thread performance CPU, 4 or less CPU threads

	Light CPU usage	High single thread usage	High multithread usage
Res: <= 1080p Settings: <= Med	No	Yes	Yes
Res: <= 1080p Settings: >= High	No	No	Yes
Res: >= 1440p Settings: <= Med	No	Yes	Yes
Res: >= 1440p Settings: >= High	No	No	Yes

 

High single thread performance CPU, 6 or more CPU threads

	Light CPU usage	High single thread usage	High multithread usage
Res: <= 1080p Settings: <= Med	No	No	No
Res: <= 1080p Settings: >= High	No	No	No
Res: >= 1440p Settings: <= Med	No	No	No
Res: >= 1440p Settings: >= High	No	No	No

 

Notes

• Resolution is the vertical resolution, regardless of horizontal resolution. So 1080p also means 2560x1080.
• The gap between 4 and 6 CPU threads is intentional. You could force a game to only use 5 CPU threads, but there's nothing avaialble as far as I know that's a 5 CPU thread processor.
• Definition of terms
  • Light CPU usage: The game was designed for lower-end systems from the get go.
  • High single thread usage: The game sees little to no benefit running on something with more than four CPU threads
  • High multithread usage: The game sees appreciable benefits running on something with more than four CPU threads

 

List of CPUs that fall into the above categories

Below are where CPUs fall into the categories that the answer table is sorted in. This was made with the following considerations:

• The processors running at stock speeds. Overclocking may help.
• Listing consumer variants only. If you have a server/workstation variant, find the closest match to a consumer CPU and go from there.
• The quick and dirty line between "low" and "high" single thread performance is if the CPU can get at least 144 FPS on low-end games (I may go back to scrutinize the line more)
• This list is by no means precise and tries to be reasonably accurate, therefore, it may change regularly.

To figure out where your CPU lies in these categories, start from the "Low Single Thread Performance." If your CPU meets one of the criteria, it's considered that. Otherwise move to the next category and so on.

 

Low Single Thread Performance

Spoiler

Intel

• Any Celeron
• Any Atom
• Any Core 2
• Any Pentium that has an operating frequency of <= 3.5GHz.
• Any Core-i3 that has an operating frequency of <= 3.5GHz.
• Any Core-i5 that has an operating frequency of <= 3.5GHz.
• Any Core-i7 that has an operating frequency of <= 3.5GHz.

AMD

• Any Athlon
• Anything in the Phenom II series
• Any FX processor
  • The FX-9590 might creep into the high performance category, but not often enough for it to count

 

High single thread performance

Spoiler

Intel

• Any Pentium that has an operating frequency of > 3.5GHz.
• Any Core-i3 that has an operating frequency of > 3.5GHz.
• Any Core-i5 that has an operating frequency of > 3.5GHz.
• Any Core-i7 that has an operating frequency of > 3.5GHz

AMD

• Any Ryzen 3
• Any Ryzen APU

 

High single thread performance, 6 or more CPU threads

Spoiler

Intel

• Any Core-i5 after the 7th gen
• Any Core-i7
• Any Core i9

AMD

• Any Ryzen 5
• Any Ryzen 7
• Any Ryzen 9
• Any Threadripper
  • Note that Threadripper's performance can vary depending on the game. I'm throwing it in this category because on paper and synthenitc benchmarks, it fits.

 

 

Partial list of games that fall into CPU usage

This is is meant to provide good enough (hopefully) sample size that you can use to figure out depending on what you play will have a bottleneck somewhere. This is not meant to be a comprehensive list so expect games that you may play to not be here. Also if the game runs with something else, such as a platform or DRM, it's factored into its CPU usage regardless.

 

Light CPU usage

Spoiler

Counter Strike: Global Offensive

Minecraft, if not hosting a server

Overwatch (maybe, going off of requirements)

Rocket League

 

High single thread usage

Spoiler

If a game was developed before 2016, chances are it'll live in this category.

 

ARMA 3

Call of Duty

Crysis (I had to put this here )

DOOM (2016) with Vulkan

Fortnite

GTAV

Metro Exodus

Monster Hunter: World

PUBG 

Shadow of the Tomb Raider

High multithread usage

Spoiler

Assassin's Creed: Odyssey

Battlefield 1

Battlefield V

Civilization 6

The Division 2

F1 2019

Final Fantasy XV

Ghost Recon: Wildlands

[Princess Luna]

Amazing OP Mira, it will certainly be useful for a quick linking on plenty of threads to come.

 

I am yet to read all of it in depth however I'd like to point just an observation to remember about dark theme users since you've used plenty of black colored font.

 

Cheers!

[Mira Yurizaki]

53 minutes ago, Princess Luna said:

I am yet to read all of it in depth however I'd like to point just an observation to remember about dark theme users since you've used plenty of black colored font.

This is what I get for copying from Google Docs.

 

I'll get to it when I can. 

[FarAwayFromTheSun]

A lot easier to just tell someone if they have a bottleneck or not or some games may show one.

[jones177]

All Systems bottleneck. 

It depends were the bottleneck is that determines if it is an issue.

 

Since I play at high resolutions I am always GPU bound. Fortunately my monitors are in the 60 to 75hz range so it is not an issue. It would be an issue if they were in the 100 to 144hz range. 

 

I do test at lower resolutions since I may buy a 1080p 240hz monitor at some point and I already bought a 1440p 144hz monitor. 

I did toss my i7 8700k because it could only get frame rate into the 130s in most of the test I did at 1440 and my i7 8086k could run all the tests over 144fps. The only difference between the 2 is that one ran at 4.8ghz and one ran at 5ghz so I would describe CPU bottlenecking as a cliff. The funny thing is I tossed the 1440p monitor as well since I prefer higher resolutions.

 

The only change I would make to the chart is to replace Metro with any Bethesda game and move Metro into the high multithreaded list.  Here is Metro hitting all threads hard at 1080p at low setting with my 6 core, 12 thread CPU.

 

By contrast here is Assassin's Creed Odyssey at 4k ultra. The CPU is cruising along but the GPU is maxed out, running hot and barely making 60fps. I usually take most of the anti aliasing off to keep the frames over 60 and take some of the pressure off the GPU.