Not utalized CPUs showing different FPS measurements?

[TechnoSword]

I've seen this in A LOT of games and it's bugging me to death. 

 

You're playing a game where none of your CPU threads are even close to 100% pegged, but some how, for some unknown reason, switching to a more powerful CPU with the same core/thread count nets you a FPS gain. Despite it also not being used more then the older one. 

 

Why the difference?!?

 

This is all assuming the rest of the hardware is consistent as possible elsewhere to- same storage, RAM amount, and GPU are used in each build. It's already been shown motherboards don't make more then a margin of error of difference (outside of synthetics and the new x99 boost clock stuff), and that RAM speed makes all of a 3% impact max in games when using a dedicated card.

 

So will someone, please, PLEASE tell me why stuff like in that video happens^

Does the game engine, or game, have some kind of internal un-optimized performance cap where it makes cache and RAM speed matter more?  

 

This is extremely confusing. Before when upgrading my CPU and seeing this- I had just assumed my FPS gain was attributed to new drivers, a lower ambient temp leaving more room for a GPU boost, ETC. That video, and ones like it, confirm that there is something else going on. What is that something else? 

 

 

[MoonlightSylv]

IPC, clock speed, and other generational improvements.

[SpaceGhostC2C]

18 minutes ago, TechnoSword said:

I've seen this in A LOT of games and it's bugging me to death. 

 

You're playing a game where none of your CPU threads are even close to 100% pegged, but some how, for some unknown reason, switching to a more powerful CPU with the same core/thread count nets you a FPS gain. Despite it also not being used more then the older one. 

 

Why the difference?!?

 

This is all assuming the rest of the hardware is consistent as possible elsewhere to- same storage, RAM amount, and GPU are used in each build. It's already been shown motherboards don't make more then a margin of error of difference (outside of synthetics and the new x99 boost clock stuff), and that RAM speed makes all of a 3% impact max in games when using a dedicated card.

 

So will someone, please, PLEASE tell me why stuff like in that video happens^

Does the game engine, or game, have some kind of internal un-optimized performance cap where it makes cache and RAM speed matter more?  

 

This is extremely confusing. Before when upgrading my CPU and seeing this- I had just assumed my FPS gain was attributed to new drivers, a lower ambient temp leaving more room for a GPU boost, ETC. That video, and ones like it, confirm that there is something else going on. What is that something else? 

 

 

First thing to do, in order to know whether there is any puzzle at all, is to look at overall CPU usage measures. The percentages you see in that video are highly misleading due to hyperthreading being enabled. How do 4 cores maxed out look like when splitting the information into 8 "logical cores"?

[SpaceGhostC2C]

1 minute ago, ShadowTechXTS said:

IPC, clock speed, and other generational improvements.

Those make a CPU faster. His question is why a faster processor makes a difference when the slowest one isn't fully utilized (assuming that is the case).

[MoonlightSylv]

2 minutes ago, SpaceGhostC2C said:

Those make a CPU faster. His question is why a faster processor makes a difference when the slowest one isn't fully utilized (assuming that is the case).

Ah, I misunderstood the question.

[pyrojoe34]

Some processes can only be done sequentially (you need the answer to one before you can start the other, physics for example), which means you have to wait for that one to finish. Say that particular calculation only takes a small amount of CPU power to do but needs a minimum number of clock cycles to run. In this case a slower CPU may only need 10% of it's capability to run it but it takes 200ms to run, now take a faster CPU that can do the same task in 150ms. You can't just use 20% of the slower CPU to cut the time in half because the task can only run once the previous task is done. This goes beyond just the multi-threading problem and can exist even in a single threaded core since not every task can use 100% of a core. Now add in other factors like how long it takes to fetch information from the cache or RAM, if there are specialized architectures within the CPU for very specific tasks (like a h.264 encoder/decoder for example), or even how far apart things are in the CPU (the speed of light is absolute) and plenty of other complex factors I don't understand and you start to see why things like cores, frequency, and even IPC or transistor count cannot always predict relative performance.

[SpaceGhostC2C]

Having skimmed through the video, I must say that the most noticeable FPS differences do coincide with heavy CPU usage.

[Jumper118]

They may have newer instructions that help it.  If you run Intel XTU on cpus you can really see this difference.  A 6600k can be massively faster than a 3930k even though both cpus are being used 100% on all thread and the 3930k has 2 more cores and ht and in the real world should be 30% faster. 

[kirashi]

It's not at all about the raw CPU speed or age so much as it's about all the memory bandwidth, bus speeds, and other technologies supported by the CPU.

If you take a look at this screenshot/excel I made from the Intel ARK site comparing the i7-6700, i7-4790, and i7-870 processors, you'll see some differences:

 

I'm no expert on technicalities of processor bandwidth, but numbers alone tell me the higher bus speed and memory bandwidth result in more FPS.

[TechnoSword]

Didn't get any emails about the responses....but yay people responded  

Glad pyrojoe34 found a realistic answer of some kind. Literally the only thing I've ever heard make any kind of sense relating to it. 

 

Always irritates me when most everyone says "oh it's the memory speed" or "oh it's the PCIe 2.0 x16 vs 3.0 x16 bandwidth". As both those have been tested extensively to not matter in comparisons like the one in the video when gaming.