Question i5-9400F refuses to boost to 4.1GHz on a single core.

[Skalavesky]

As expected, on all 6 cores, the speed never goes above 3.89GHz, which is normal.

However, I expected it would reach the advertised 4.1GHz on a single core, but if I run a benchmark of some sort, it will only go to 4.08GHz max, never above that.

Is this expected behavior?

 

[RememberThe5th]

Well there is thing called Bus clock aka. BCLK.
Bus clock (speed, 100.16Mhz) which multiplies with your multiplier (X36) = your clock speed (3605.60Mhz)

You may set your Bus clock in settings to keep that 100 (by setting it to high).
But thats quite normal.
Some motherboards tend to do 99.98Mhz some tend to be 101Mhz.
Also this Bus speed is connected to every M.2, Sata and PCIe speed (excluding Ram, its not 2006 with 775/1366 socket)
Soo fiddling with it might result in crashes , but devices tend to tolerate 5Mhz without issue.

 

[TerryLaze]

As expected, on all 6 cores, the speed never goes above 3.89GHz, which is normal.

However, I expected it would reach the advertised 4.1GHz on a single core, but if I run a benchmark of some sort, it will only go to 4.08GHz max, never above that.

Is this expected behavior?

Different software uses different amounts of CPU 4.1 is only guaranteed for low demanding software, the fact that you get 4.08 on any kind of benchmark is very good since benchmarks are made to use as much of a CPU as possible, try with something less demanding like a game or something.
Although 200Mhz less is nothing to cry about.

 

[Skalavesky]

Different software uses different amounts of CPU 4.1 is only guaranteed for low demanding software, the fact that you get 4.08 on any kind of benchmark is very good since benchmarks are made to use as much of a CPU as possible, try with something less demanding like a game or something.
Although 200Mhz less is nothing to cry about.

I used CoreTemp to monitor the clock speed instead of Windows Task Manager... It did boost to 4.1GHz very, very briefly. For less than one second. But it did.

I thought Turbo Boost was constant, but that's not the case and the processor will only boost to its full speed if really needed.
It doesn't go up to 4100MHz because it doesn't need to. Thanks!