CPU as bottleneck

So I know that when GPU is the bottleneck in games it can result in FPS lag and such, but when CPU is bottleneck does the same thing happen?

 

Yes, check out GTA4. That's exactly what happens there.

 

CPU bottlenecks in 2 circumstances:

- your GPU is significantly strong and your CPU is very very weak(which isn't a given since for most situations, a 2.0GHz core 2 duo should manage most games)

- your game is very intensive for the CPU such as RTS games(where lots of calculations need to be done) or games with lots of engaged physics(such as calculating distances and speeds) like Flight Simulators. GTA4 is also to add to the list of CPU-demanding games

In general, the chances of your CPU being the bottleneck are quite low if you have a decently balanced system and it'll mostly be the game which will dictate the bottleneck.

 

The other posters in this thread did a nice job of covering when you will have a CPU bottleneck.

Yes - if the game is very CPU intensive and your system is not up to par, you will have stuttering/lag just the same.

 

If task manager says 100% cpu usage then it is the bottle neck (or bad software)

 

My computer is the P-7801u and from what I've heard the GPU is strong yet the CPU is weak. Because I usually only play RTS, I was hoping that it could run Empire: Total War at max settings. Could it still do that without any lag?

 

I can play CnC3 on my lappy

Mind you, it's only on low because my GPU has some issues.

 

Settings shouldn't influence lag that much as they are the GPU's job. It's when lots of things will start popping on the map that you'll experience lag due to your CPU. Oh and connection will affect lag on multiplayer of course.

In fact, connection IS usually the biggest lag factor on multiplayer games. People sometimes forget this factor. I've lagged on WC3 with a dual core CPU and a desktop HD4850 because of crappy connection that day

 

Total War is going to lag for sure. If there is any question about the CPU it won't be able to go max. Google benchmarks for I7's and quad cores with Total War and see how poorly they do at high settings. It is calculating every bullet :-/

 

Don't forget the Source engine games - they're more CPU-intensive than other games. I can definitely confirm that TF2 is CPU-limited.

 

Interesting read:
http://forum.notebookreview.com/showthread.php?t=122013

 

I thought that was a non-multi-core support issue? Most Source games usually run upwards of 100 FPS without AA on a good graphics card at medium resolutions.

 

A bottleneck is when one component is limiting another component. GPU's can never really be a bottleneck, but because ALL data passes through the CPU before going to the GPU, the CPU is often limiting the capability of the GPU. In RTS games the CPU usually has to do hundreds of AI simulations as well as physics and process what data is sent to the GPU for further rendering. It's typically easy to spot if the CPU is bottlenecking the GPU by putting a slight amount of load on the CPU, or overclocking/underclocking it slightly and checking your framerate gains/losses.

Source engine games usually have a LOT of particle effects, especially TF2, which are calculated on the CPU, which is why enabling multi core in TF2 grants such a massive framerate increase.

 

Strategy games use cpu a lot!!! Like when i used to play dota.

 

Any strategy game can bring most CPU's to their knees if the map is crammed with enough units. Games as far back as Total Annhilation could do this.

 

In simpler games, however, you don't need the CPU to run high. I've played Empire at War with a limit of 800 MHz without any hiccups.