[SOLVED] Does PBO's overclock frequency apply to all cores?

[Iver Hicarte]

Good day,

This question just popped out of my head, if PBO (the automatic overclocking feature of AMD) is enabled on Ryzen processors, does it mean that the overclock frequency that PBO can provide the CPU apply to all cores? For example, if the PBO feature enables the 5900x to reach 4.5ghz, is this frequency applied to all cores? Or is it only applied to a certain core? I mean if all cores run at 4.5ghz, wouldn't that be too hot and would require too much power and voltage for coolers and for the motherboard to handle?

Thanks.

 

[TommyTwoTone66]

It should intelligently pick the 2 most loaded cores to overclock. You're right, it would not boost all cores to max at the same time, that would generate too much heat and draw too much power.

 

[drea.drechsler]

Good day,

This question just popped out of my head, if PBO (the automatic overclocking feature of AMD) is enabled on Ryzen processors, does it mean that the overclock frequency that PBO can provide the CPU apply to all cores? For example, if the PBO feature enables the 5900x to reach 4.5ghz, is this frequency applied to all cores? Or is it only applied to a certain core? I mean if all cores run at 4.5ghz, wouldn't that be too hot and would require too much power and voltage for coolers and for the motherboard to handle?

Thanks.

You misunderstand what PBO does as it does not alter clock frequency directly.

Normally, the boost algorithm will boost core clock frequencies based on available margins in certain parameters which include thermal margin and available power and current delivery margin from the VRM. What PBO does is it opens the margins for power and current (PPT, TDC and EDC) to allow the algorithm to go further. But it's still limited by temperature so if thermal margin isn't sufficient it won't boost as high as it might. Really good cooling pays off with PBO being able to work better.

That's also the 'auto-overclock' settings but what it does is extend the target frequencies the algorithm can use. What that means is still a mystery to me as nobody's written much on just what that means. But I don't think there's any kind of guaranteed automatic response: use a 200Mhz AutoOC setting and it generally does not automatically respond by boost 200Mhz higher.

But, as far as core boosting: the 'better' cores have better leakage currents, among other things intrinsic to the silicon and process. So they run cooler, since they're running cooler they can boost a slight bit higher at the same temps so the algorithm responds accordingly.

PBO2, available with Zen 3, also add curve optimizer. That allows you to slightly alter the voltage curve used by the algorithm. It can be quite dramatic, although I lack a 5000 CPU myself to play with. Undervolting with offsets along with the Optimizer affects voltage, current therefore power and thermals allowing even higher boosting. And this affects all cores, although I'm not sure it boosts all cores to maximum clocks simultaneously and some cores will be better than others.