CPU Usage vs Frequency, looking for clarification.

[SpaceJellyDonut]

Hi, I'm looking for an explanation on what happens when a CPU is at different percentages of use at maximum clock speeds. 

 

So I understand that a CPU can increase it's clock speed to process information more quickly. But what happens when a CPU is at its maximum frequency (let's say 3.6 GHz) and it can't go any higher, where its usage is at either 50% or 100%. If the CPU cannot increase its speed any more, how is it processing more or less information but staying at the same frequency? 

 

So as an example, I could be running a certain game where the CPU is at 3.6 GHz (its maximum speed) but the usage says that each core's usage is between 30%-50%, now I fire up another game that requires more processing power where the CPU is still at its maximum frequency (3.6 GHz) but now each core's usage is between 80%-100%. 

 

What is happening inside the processor that its able to increase the amount of processing done while still being at the same speed? 

 

Sorry if the question doesn't make any sense, I'm not sure how to ask it differently.  

[GoldenLag]

It utilization. 

 

With low utilization in a single core there is a lot of idle-clocks where nothing is done. 

 

Essentially the percentile is showing how many of the clocks are actually doing something

[Master Disaster]

Frequency is not the ultimate measure of how much work, that would be IPS or more precisely it's Frequency X IPC = IPS.

 

https://en.m.wikipedia.org/wiki/Instructions_per_cycle

 

Basically the CPU can still cycle at 3600000 times per second while it's not actually doing any work during those cycles.

 

Think of it like revving an engine while the gearbox is in neutral, the engine is running but the rest of the car is doing nothing but as soon as you engage the gearbox that work is converted into movement

[SkilledRebuilds]

CPU Usage is the amount of TOTAL INSTRUCTIONs at any given time.
 

Lower clocks (same CPU) higher Usages because the Instructions have not changed in demands,..

Also depends on threading as you'd just assume every thread is working equally when it's likely got variance to it as well.

[SpaceJellyDonut]

So using the car engine analogy, revving the engine up to a maximum of 8000 RPM while being in neutral would be like a CPU running at maximum frequency but none of the clock cycles are being used to process anything? 

 

When I was pondering this subject I would never have thought about the actual clock cycles each being its own thing that can be used.

 

Thanks a lot for the clarification, if someone ever asks me about this subject at least now I'll be of some use however little. 

 

 

[Mister Woof]

My manual OC has my chip at 5ghz all the time but it is 1% utilization and only pulling around 15ish watts at idle

[IAmAndre]

So I'm reviving this old topic because I have a similar question: I'm rendering videos and I can see that my CPU is running at its boost clock, so a stable 4GHZ (it's a 2600X) but the utilization is always between 50 and 80%, actually closer to the 50% most of the time. Does that mean that the rendering software isn't optimized or something?