Effective clock vs instant (discrete) clock

CodeZ1LLa

New Member
Exactly! :) Moreover to read the actual multi the core needs to wake-up, which introduces the observer effect.
Hi, Martin!
May I ask you: how an "effective clock" looks programmatically? I just started to dig it for my project, and I use MSR to get values.
In my case, the results are slightly different than what HWInfo shows as an effective clock despite I tried to reproduce the logic as accurately as possible based on your explanation.
If it's not a secret (it's totally understandable if it is), can you PM me a snippet, pseudo, or some sort of formula?
Thank you in advance!
 

Martin

HWiNFO Author
Staff member
Hi, Martin!
May I ask you: how an "effective clock" looks programmatically? I just started to dig it for my project, and I use MSR to get values.
In my case, the results are slightly different than what HWInfo shows as an effective clock despite I tried to reproduce the logic as accurately as possible based on your explanation.
If it's not a secret (it's totally understandable if it is), can you PM me a snippet, pseudo, or some sort of formula?
Thank you in advance!

It's based on the APERF counter (delta), but even if you would implement the exactly same method as HWiNFO, you'd get somewhat different results due to different sampling points/intervals.
In some cases (i.e. AMD Zen with Snapshot Polling enabled) a different method is used that cannot be disclosed.
 

Zalinisto

New Member
Hey Martin,

I have a Ryzen 2700X and when I expand the Core Effective Clocks tab I noticed that all 8 cores have a T0 and a T1 Effective Clock. After reading through this entire thread and creating an account it dawned on me that I might be seeing the physical and SMT threads. Is this correct?

Thanks!
 

Martin

HWiNFO Author
Staff member
Hey Martin,

I have a Ryzen 2700X and when I expand the Core Effective Clocks tab I noticed that all 8 cores have a T0 and a T1 Effective Clock. After reading through this entire thread and creating an account it dawned on me that I might be seeing the physical and SMT threads. Is this correct?

Thanks!

Yes, T0 is what you call the "physical" and "T1" the respective SMT thread.
 
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