Question [AMD] Cannot turn off "Precision Boost Overdrive" in BIOS

Oct 20, 2019
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I want to turn off Precision Boost Overdrive for my Ryzen 9 3900X and Ryzen 7 3700X.
Just one slight problem, no matter what I do, it won't turn off.

Precision Boost is disabled in BIOS under AMD Overclocking>Precision Boost Overdrive.
It's also disabled under AMD CBS>XFR Enhancement.

Yet it still boosts to turbo frequencies.
This problem happens on both CPUs with different motherboards.

Motherboard (1): ASRock X570 Taichi
Motherboard (2): Gigabyte X570 Gaming X

This is driving me nuts, tried every released BIOS version on both motherboards with no luck.
 
Those processors feature a capability called "Boost" that automatically overclocks the CPU beyond the nominal "Base" clock frequency provided certain conditions related to thread count, power draw, and temperatures are met.

Precision Boost Overdrive

PBO does not ever do is boost the CPU frequency beyond the advertised CPU clocks.

PBO only affects these three power limits.
Package Power Tracking (“PPT”)
Thermal Design Current (“TDC”)
Electrical Design Current (“EDC”)

The effect on CPU clock speed is indirect, and PBO will never boost the CPU past the advertised clocks. At best it will allow the CPU to maintain boost clocks longer and more often.
 
I want to turn off Precision Boost Overdrive for my Ryzen 9 3900X and Ryzen 7 3700X.
Just one slight problem, no matter what I do, it won't turn off.

Precision Boost is disabled in BIOS under AMD Overclocking>Precision Boost Overdrive.
It's also disabled under AMD CBS>XFR Enhancement.

Yet it still boosts to turbo frequencies.
This problem happens on both CPUs with different motherboards.

Motherboard (1): ASRock X570 Taichi
Motherboard (2): Gigabyte X570 Gaming X

This is driving me nuts, tried every released BIOS version on both motherboards with no luck.
I think you're confusing Precision Boost Overdrive with Precision Boost. Precision Boost is the AMD term for it's turbo boosting technology. Precision Boost Overdrive, or PBO, is the feature that let's you 'overdrive' it, or force it to exceed rated parameters of the CPU and/or motherboard. That doesn't mean it will exceed rated max boost clocks but it will boost to higher intermediate clocks, those between the base clock and rated max clock, and/or stay there longer.

To turn off Precision Boosting you could set a fixed, manual clock speed. If you really want that for some reason then change the CPU Multiplier setting from AUTO to 36.0 for the 3700X and 39.0 for the 3900X. That will fix clock speeds at their rated base speeds and no more boosting.

File this under 'how to cripple a Ryzen 3000'.
 
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Oct 20, 2019
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See this post: PBO explained

Essentially there is no reason to turn it off. Simply keep your processor base clocks at or below max rated and PBO will not affect it.
I want to run cool and quiet as possible, thats why. The performance loss isn't a huge issue for me.
So there is a reason for me.

To turn off Precision Boosting you could set a fixed, manual clock speed. If you really want that for some reason then change the CPU Multiplier setting from AUTO to 36.0 for the 3700X and 39.0 for the 3900X. That will fix clock speeds at their rated base speeds and no more boosting.
Ok I got some clarification atleast however, the problem with setting the fixed clock speed is that it refuses to clock down when idle.

Is there a way to fix this?
 
I want to run cool and quiet as possible, thats why. The performance loss isn't a huge issue for me.
So there is a reason for me.


Ok I got some clarification atleast however, the problem with setting the fixed clock speed is that it refuses to clock down when idle.

Is there a way to fix this?
Cores will still go into a 'deep sleep' state when idle. You won't be able to see it, though, as monitoring programs report the last core clock speed before going into the sleep state in order to not wake the core; polling the core wakes it.

What you can see is the lowered voltage, it should go down to 1.0 volt --less actually-- when idle. To see this use HWInfo64 and monitor the VCore (STI2 TFN) voltage, which is the most correct core voltage reported by the processor from telemetry.

Going further down the path of crippling the CPU, you could also disable SMT and then disable cores to lower power consumption even more. But that does get interesting... as cores drop the remaining ones work harder to do the routine housekeeping Windows needs. That might increase thermal output, of those cores at least.

But another strategy that would use some of Ryzen's features would be to lower Vcore using offsets. With a lowered VCore the algorithm will maintain stability by lowering it's actual boost performance. It's been reported as a phenomenon called 'clock compression', it seems to be boosting as before but it's not really. Actual performance goes down, as does power consumption.
 
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Oct 20, 2019
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Cores will still go into a 'deep sleep' state when idle. You won't be able to see it, though, as monitoring programs report the last core clock speed before going into the sleep state in order to not wake the core; polling the core wakes it.
What you can see is the lowered voltage, it should go down to 1.0 volt --less actually-- when idle. To see this use HWInfo64 and monitor the VCore (STI2 TFN) voltage, which is the most correct core voltage reported by the processor from telemetry.
Voltage won't go under 1.3v even in idle when set to automatic with fixed clock freq.
HWInfo64, HWMonitor, CPU-Z, AMD Ryzen Master and other programs all show the same.
I've also measured with a multimeter confirming that the voltage isn't going down.

Going further down the path of crippling the CPU, you could also disable SMT and then disable cores to lower power consumption even more. But that does get interesting... as cores drop the remaining ones work harder to do the routine housekeeping Windows needs. That might increase thermal output, of those cores at least.
Disabling SMT defeats the purpose I got the CPU for, I do actually need all threads but not the turbo boost for the Ryzen 9 3900x.

But another strategy that would use some of Ryzen's features would be to lower Vcore using offsets. With a lowered VCore the algorithm will maintain stability by lowering it's actual boost performance. It's been reported as a phenomenon called 'clock compression', it seems to be boosting as before but it's not really. Actual performance goes down, as does power consumption.
Offset voltage refuses to work on the ASRock X570 Taichi with the Ryzen 9 3900X, no matter what I put in as either - or +. Confirmed by measuring with the multimeter again.

Works on the Gigabyte X570 Gaming X with Ryzen 7 3700X though, but still won't lower the voltage during "sleep".
 
Voltage won't go under 1.3v even in idle when set to automatic with fixed clock freq.
HWInfo64, HWMonitor, CPU-Z, AMD Ryzen Master and other programs all show the same.
I've also measured with a multimeter confirming that the voltage isn't going down.
....
Wow... my B450M mortar, with 3700X at a fixed multiplier of 36.0 and VCore setting to AUTO, is dropping to .2-.3 volt range when idle. And I can quite merrily dial in negative offsets, although I don't do it because I'm not interested in gimping performance. It's a very power efficient processor left to it's own devices, so I'm content with that.

One other thing: in latest HWInfo there's an entirely new section in the sensors screens devoted to Core/Thread effective clock speed. The shows an effective clock speed of the threads, averaged across a time period, to show the effect of sleep states which drop clock speeds to 0. You might refer to that to see to what extent your processor is benefiting from deep sleep states.

Martin (HWInfo's author) discusses Effective Clock speed in somewhat detail here:
in case you're interested.
 

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