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Core i5 8500 single core turbo boost

Kikovic

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#1
Hello,

I am running a core i5 8500 in my pc. The advertised speeds of this cpu are 4.1ghz single core boost and 3.9ghz all core boost. However in single core my cpu never climbs higher than 4ghz. Do i have a bad sample?
Is this something normal? Anyone else got this? I paid for a 8500 not a 8400 who single core boost is 4.0ghz. In all core boost i am getting 3.9ghz so that at least is normal.
I have already set my bios to defaults but nothing changes. I tried different program's to monitor the speed. Hwmonitor, cpu-z, core temp. They al report 4ghz max on single core. I tried testing single core with cinebench. Cpu-z even says that the multiplier is between x8 and x41 but he never does x41. Any ideas?
Thanks!
 

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#2
Have you checked the CPU temperatures?
 
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Kikovic

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#3
Yes, temps never exceed 55degrees. My cpu is cooled with an Scythe Mugen 5 Rev. B.
 
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#4
It will only ever hit 4.1 when you’re using that one core with Windows, I’d imagine. Your three other cores don’t just become inactive when you use the single core benchmark. Windows will schedule tasks on the other cores which makes it difficult to only ever use one core. Your CPU is operating normally. Blame Windows and the task scheduler.
 

Kikovic

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#5
It will only ever hit 4.1 when you’re using that one core with Windows, I’d imagine. Your three other cores don’t just become inactive when you use the single core benchmark. Windows will schedule tasks on the other cores which makes it difficult to only ever use one core. Your CPU is operating normally. Blame Windows and the task scheduler.
Well i let him go into full idle when the speed is down to 800mhz. Then i test single core speed but it never reaches 4.1ghz. I have tested with other cpu like a Ryzen and then i have no problem to reach single core turbo.
 
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#6
You could try high performance power mode in windows.
What is your motherboard?
 
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#8
Motherboard is ASUS Z370 Tuf Gaming Pro. I have not tried high performance, my power mode is balanced at the time. I'll give it a try.
The behavior you should see is:


Turbo Frequency
4,100 MHz (1 core),
4,000 MHz (2 cores),
4,000 MHz (3 cores),
4,000 MHz (4 cores),
3,900 MHz (5 cores),
3,900 MHz (6 cores)

Its likely it always wants to use 2 cores so you never see the 4.1.


The i5 8400 has the following turbo
4,000 MHz (1 core),
3,900 MHz (2 cores),
3,900 MHz (3 cores),
3,900 MHz (4 cores),
3,800 MHz (5 cores),
3,800 MHz (6 cores)

So you are still getting a benefit of 100 MHz over the 8400.
 
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Kikovic

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#9
The behavior you should see is:


Turbo Frequency
4,100 MHz (1 core),
4,000 MHz (2 cores),
4,000 MHz (3 cores),
4,000 MHz (4 cores),
3,900 MHz (5 cores),
3,900 MHz (6 cores)

Its likely it always wants to use 2 cores so you never see the 4.1.


The i5 8400 has the following turbo
4,000 MHz (1 core),
3,900 MHz (2 cores),
3,900 MHz (3 cores),
3,900 MHz (4 cores),
3,800 MHz (5 cores),
3,800 MHz (6 cores)

So you are still getting a benefit of 100 MHz over the 8400.
Ok thanks.

All the other speeds are correct. Only the single core turbo i'm not getting 4.1.
So you think i'm good? And the chip is not faulty?

All core boost is 3.9ghz, so yes i'm getting 100mhz benefit over the 8400 when he uses all cores.
 
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#10
I always run my PC on high performance mode.

Also you can try overlcocking the bus clock in bios to 102.5 - its generally safe nothing higher than that though, and that will give you 4.2 ghz all 4 cores, and if your bios has something like - set all turbo on, its named a lot of different things... turn that on too, and you will get 4.2ghz 24.7 no downlocking. :D
 
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#11
I note the Intel ARK says "up to" 4.1GHz. :wtf:

If it was stuck at 3.9GHz, then you might have a bad sample. I think yours if fine so I personally would not worry about it. But if I were worried, I would try that processor on a different motherboard to see with it did there. This could just be a minor (very minor) issue with voltages and/or monitoring.
 
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#12
Im running a i5-8400 and it pretty much never runs at 4 GHz, even during single core load only. 99% of the time under any kind of load it just stays at 3.9 GHz.
 
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#13
Ok thanks.

All the other speeds are correct. Only the single core turbo i'm not getting 4.1.
So you think i'm good? And the chip is not faulty?

All core boost is 3.9ghz, so yes i'm getting 100mhz benefit over the 8400 when he uses all cores.
You are getting the expected performance. The extra clock speed is fairly meaningless for performance anyway so don't stress over it. I can't tell a difference between an i5 8400 and an 8600k@5 GHz.
 
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#14
Start prime 95 small fft then goto task manager and set affinity to prime95 only to core 0.
 

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#16
Ok thanks.

All the other speeds are correct. Only the single core turbo i'm not getting 4.1.
So you think i'm good? And the chip is not faulty?

All core boost is 3.9ghz, so yes i'm getting 100mhz benefit over the 8400 when he uses all cores.
You almost never see a true single core load anymore, so you'll likely never see the 4.1GHz. There is always something going on in the background.

I bet if you left HWMonitor running, you'd see the max clock speed hit 4.1GHz(or actually more likely ~4.095GHz due to the BCLK not being a perfect 100), but it just happens so rarely and so fast that most of the time you won't even see it happen. And most monitoring programs don't update fast enough to see when it does happen, but leaving HWMonitor open for a long period of time means you have a good change that it will update right at the right time and catch it at 4.1GHz.
 
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#17
HWiNFO is a good tool as well. From what I gather, the way turbo boost works, the CPU could only be hitting 4.1 in very brief bursts, so a sustained load could actually keep you from reaching it.
 

user112

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#18
try to disable turbo boost plus any sleep states and adjust voltage/cache a little then lock it to 4.1Ghz in your bios settings.though you should test the voltage/cache adjustments in intel XTU before doing them in the bios. also I wouldn't mess with bus clocks since some interfaces like SATA don't like it when you do that.
 
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