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3.1ghz base, 4.3 boost, showing 3.5ghz running prime 95, why?

3080guy

3080guy

3080guy

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26 Sep 2020
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221
Ive got an AMD 3900 pro 3.1/4.3ghz processor
https://www.amd.com/en/products/cpu/amd-ryzen-9-pro-3900

And a MSI B450 A Pro Max Motherboard
https://www.msi.com/Motherboard/B450-A-PRO-MAX/Specification

Running prime95 which I downloaded today, my processor (in task manager) shows 2.5 to 3.7ghz at 100% load and sometimes wont go above 85% load.

During all of the above, CPU temp varies from 55c to 65c (in afterburner).

Why does CPU never reach 4.3ghz, its boost max, and why is temp so low with the processor only hitting 3.87 max?

I recently updated my bios.
Ive never run prime 95 until today.
Friend said I should be hitting 4.3ghz and something is wrong. Cant be thermal throttling (wherever that is controlled?) as my CPU is running cool, in the high 50s. Help appreciated.
 
Max boost is usually just single core, opportunistic boost with burst workloads. Prime95 works all cores which will not ever let you hit near max boost frequencies.

The temps seem fine for 3.7GHz, they're extremely efficient at lower clock speeds. I have the 3900x which has higher clocks, it boosts to 4.6GHz with light loads and all-core loads are usually around 4-4.1GHz at stock. Manual overclocks can net 4.4 to 4.5GHz on a good CPU.
 
It is a 65W TDP chip running 12 cores. Impressed it is even running at 3.7ghz at intense load.

Given it can't be overclocked, it might not even get the 88W precision boost normally gives for 65W chips.

It's running cool because it is power limited.

3900X for reference is a 105W chip with 142W with precision boost.
 
As muon says its a 65w TDP chip so the CPU will adjust clocks depending on how heavy the load is to keep within that 65w limit.

You can increase the limit by Raising PPT TDC EDC.
 
andy_mk3 said:
Max boost is usually just single core, opportunistic boost with burst workloads. Prime95 works all cores which will not ever let you hit near max boost frequencies.
Click to expand...
Are you saying only one core will boost ultra high for a short time? Is the figure given an average of all cores?
 
muon said:
It is a 65W TDP chip running 12 cores. Impressed it is even running at 3.7ghz at intense load.

Given it can't be overclocked, it might not even get the 88W precision boost normally gives for 65W chips.

It's running cool because it is power limited.

3900X for reference is a 105W chip with 142W with precision boost.
Click to expand...
Right, so... the low figure Im getting is on account of low power availability.
Ill have to look up what precision boost is. Thanks for this info.
 
Joxeon said:
As muon says its a 65w TDP chip so the CPU will adjust clocks depending on how heavy the load is to keep within that 65w limit.

You can increase the limit by Raising PPT TDC EDC.
Click to expand...
I dont have the knowlege at this point. It sounds like my chip isnt as fast - nor can it be, as the 3900x. Never overclocked a CPU, Ive only managed some mild XMP profile tweaks.
 
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