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Understanding Precision Boost Overdrive in Three Easy Steps

Staff
Staff
5 25 122K

Precision Boost Overdrive (PBO) is a powerful new feature of the 2nd Gen AMD Ryzen™ Threadripper™ CPUs.1 Much like traditional overclocking, PBO is designed to improve multithreaded performance. But unlike traditional overclocking, Precision Boost Overdrive preserves all the automated intelligence built into a smart CPU like Ryzen: Precision Boost 2 remains enabled for on-demand performance, XFR 2 still enables higher performance with better cooling, and the CPU still lowers clocks and voltages to save power at idle. As you can see, Precision Boost Overdrive is sort of a “best of all worlds” approach to overclocking that manual mode usually doesn’t offer. But how does PBO work? Let’s find out in three easy steps.

Step 1: What Controls Boost

All 2nd Gen AMD Ryzen-branded Processors use Precision Boost 2, which intelligently leverages a large network of sensors built into the CPU to determine whether it’s okay to boost. These sensors measure and react in a very fast loop: up to 1000 times per second. Though there are many data points being measured, the most important are:

  • SoC Power (“PPT Limit”): measured in watts, the amount of power the CPU can draw before boost levels off
  • VRM Current (“TDC Limit”): measured in amps, the amount of current we let the motherboard deliver to the CPU before boost levels off
  • Temp (°C): measured in degrees Celsius, the temperature the CPU can reach before boost levels off

If the sensors detect that the CPU isn’t close to one of these limits, Precision Boost 2 sees opportunity to raise clockspeeds on as many cores as it can.

It is useful to imagine these three thresholds (“platform limits”) as a triangle, shown below, where the labeled corners are something like the RPM redline on your car. Inside of that, a safer and more reliable triangle that represents the factory configuration of your CPU.

pastedImage_7.pngFigure 1: Precision Boost 2 leverages extra thermal and electrical capacity to enable higher performance. The CPU’s factory configuration is aggressive, without pushing the CPU to the red line in power or temperatures.

Step 2: More Room to Play

If the size of the imaginary triangle largely determines whether or not the CPU can boost, what if the triangle were simply larger? In the previous diagram, you may have noticed that there’s some empty space between the factory CPU configuration and the platform limits. That empty space is what users are filling up when they overclock their CPU, and it’s the same space the 2nd Gen AMD Ryzen Threadripper CPU consumes when PBO is enabled. Let’s see how that new triangle might look!

pastedImage_18.pngFigure 2: Precision Boost Overdrive gives Precision Boost 2 more "room to play" before pulling back on boost. More cores, more frequency, more often!

As you can see, the PPT and TDC Limits have been embiggened to let the platform draw more power. That extra power is directly converted into higher average clockspeeds on more cores for a longer period of time. PBO even communicates with your motherboard to understand how much extra VRM current capacity (TDC) it can provide!

Step 3: The Benefits of Precision Boost Overdrive

By now we know that Precision Boost Overdrive unleashes a more aggressive version of Precision Boost 2 that preserves the smart frequency and voltage management that users like. The performance upside for PBO can be significant: up to 13% more multithread performance!2 That’s not dissimilar to what a user might gain with manual overclocking, but PBO can accomplish it at the touch of a button in the latest version of AMD Ryzen™ Master.

pastedImage_47.png

Precision Boost Overdrive: A Smarter Way to Overclock

Taking your feedback seriously is a critical objective for us, as is using the Ryzen CPU's intelligence in new and beneficial ways. We knew we could bring those two goals together with Precision Boost Overdrive! The result is awesome: a new type of overclocking that combines smart boost control, idle power savings, factory max boost clock, and higher nT performance. We hope you enjoy!


Robert Hallock is a technical marketing guy for AMD's CPU division. His postings are his own opinions and may not represent AMD’s positions, strategies or opinions. Links to third party sites are provided for convenience and unless explicitly stated, AMD is not responsible for the contents of such linked sites and no endorsement is implied.

Footnotes:

1. Precision Boost Overdrive requires a 2nd Gen AMD Ryzen™ Threadripper processor with AMD X399 chipset motherboard. Because Precision Boost Overdrive enables operation of the processor outside of specifications and in excess of factory settings, use of the feature invalidates the AMD product warranty and may also void warranties offered by the system manufacturer or retailer. GD-128

2. Testing conducted by AMD Performance Labs as of 7/16/2018. “Multithread performance” defined as Cinebench R15 nT. Results presented in order of Precision Boost Overdrive OFF vs. ON: 5096 vs. 5795 (%13 faster). AMD System configuration: AMD Ryzen™ Threadripper™ 2990WX, Enermax 360 CLC @ 20°C ambient temperature, 4x8GB DDR4-3200 (14-14-14-28-1T), Asus Zenith X399 Extreme (BIOS 0008), GeForce GTX 1080 Ti (driver 398.36), Windows® 10 x64 1803, Samsung 850 Pro SSD, Western Digital Black 2TB HDD. Results may vary with system configuration. Precision Boost Overdrive requires a 2nd Gen AMD Ryzen™ Threadripper processor with AMD X399 chipset motherboard. Because Precision Boost Overdrive enables operation of the processor outside of specifications and in excess of factory settings, use of the feature invalidates the AMD product warranty and may also void warranties offered by the system manufacturer or retailer. 

25 Comments
Adept II
Adept II

Thanks for the explanation. This is very cool.

Journeyman III
Journeyman III

Thank you for explaining..

Miniboss
Miniboss

Thanks for the info!

Journeyman III
Journeyman III

Thanks for this, really helpful!
You said that only PPT, TDC and temp are taken into consideration when boosting. Can you then explain, please, what EDC means in the Ryzen Master screen? Is it not taken into consideration when boosting?

Adept II
Adept II

would also like to know more abou EDC

Journeyman III
Journeyman III

I would like to know if PBO has been officially removed from the lastest agesas for AM4 and why it has been done silently. For Zen 12 nm launch every review had PBO enabled, now it seems if AMD just dropped support for it without any official statement.

Some vendors have created their own versions of the PBO but it doesn't works the same.

Journeyman III
Journeyman III

Played around a bit on a 2950x and x399 taichi this works really well.   Even being stuck with a temperature limit of 68C. 

Adept I
Adept I

My 2600X boosts to 4.25GHz consistently regardless of low ambient temps (10C), high quality motherboard & PSU. I have efficient after market cpu air cooler too but how can I get it to boost to 4.35GHz consistently?

It just seems to me that regardless of ambient temps even as low as 10C & a well ventilated closed case, it just doesn't go over 4.25GHz whilst I'm gaming.

Adept I
Adept I

My part of the world is moving into warmer seasons now & ambient temps are rising accordingly. Even with 18 -20 C, my system still only boosts to 4.25GHz typically whilst under load.

So in that respect, if ambient temps play a part in XFR 2 boost system, then it looks like at this point that below 10 C or over 20 C "might" see a difference.
But I'm sceptical.

Adept II
Adept II

What cooler are you using exactly?  What is it's rated TDP? Is it a really good one like a high end Noctua with a 200W TDP or something lower?

What about the TIM? Is it a good one, is it well applied?

Ambient air temperature is more likely to become a factor if you have e.g. a high-end liquid cooler installed as the air going through the radiator will be warmer/colder and effect the radiator's ability to dump heat rather than the rest of the system's ability to take the heat off the CPU and carry it to the radiator.

If you are using a lower-spec air cooler, it may not be able to cool the chip enough (dissipate the heat fast enough) that the ambient air temp is a noticeable factor.

Also, is the 4.35GHz supposed to be all-core?  What load are you using? How many threads? Have you tried a single-thread test to see if that shows the 4.35GHz?

Adept I
Adept I

nemesis.ie here is a link to my system specs on this AMD website > Daily gamer

My TIM is 'thermal grizzly Aeronaut'. It's well applied, I have nearly 20 yrs experience with these matters on many systems over that time so I know what I am doing in this dept.

I have had the system up to 4.45GHz - all cores & SMT, manual OC & booting into windows running benchmark apps.

Imo, the XFR 2 algorithm is set to certain parameters & when hit that 'wall'. The technology levels out.

Adept II
Adept II

@alwayshope

I wasn't trying to imply you didn't know what you were doing, just looking for clarification.

I'm at this stuff for over 30 years but that doesn't necessarily mean I'm any better or worse than you are.

I don't actually see the TDP of that cooler on the CM data sheet.

Manual OC will obviously ignore any PB limits and indeed possibly safety limits.

Is it maybe a B450 limitation or that UEFI on that board I wonder?

A liquid system would be better able to cope with sudden heat dump than an air cooler I suspect too, i.e. the temperature will not rise as suddenly when there is a boost.

Some clarification from AMD on this and indeed how well PB XFR works on the B450 vs e.g. an X470 would be good info to get.

Journeyman III
Journeyman III

Wait. According to that link, you've got an Ryzen 5 2600X. That CPU does not boost into 4.35Ghz. The Ryzen 7 2700X does. If you read the specifications (2nd Gen Ryzen™ 5 2600X Desktop Processor | AMD ), you'll see that the max boost clock is 4.2Ghz for that processor.

Journeyman III
Journeyman III

Some motherboards offer PBO on the BIOS itself. Even mine (B350 chipset) offers that. I've not checked if it was disabled after the introduction of 2nd gen Threadripper tho.

Adept I
Adept I

That CM cooler has been modded by me with better fans eg. higher cfm & combined with a tower case full of 140mm fans, I consider the air circulation around the whole system more than adequate for a daily OC.

I also have a Cryorig R1 Ultimate ready to go with AM4 kit in case this one doesn't cut it in our upcoming & infamous hot Aussie summer.

Had experience with H20 coolers yrs ago, I don't trust water near electricals & I'm not prepared to waste more $ on thermal solutions atm anyway.

I don't think it's the chipset limitation that is hindering XFR2 from raising further. I mean the MSI board I use has some of the best VRM implementation out there on the market atm.

Interestingly I checked the XFR2 boost whilst gaming with another system monitoring app yesterday reaching over 4.5GHz boost! & this is from an app that is regularly updated.

So I don't know what's going on here, in game you can't tell, because of 60Hz limitation on my monitor. But in a game like FO4, it's engine is heavily influenced by CPU power.  That game engine just loves lost of threads...

Adept II
Adept II

Interesting that you saw 4.5GHz, that's impressive and also bodes well for Zen 2 peaks in low-thread operation.

My guess based on that is that the algorithm will only allow the higher boosts for short periods due to the likely higher voltage needed and when there is a constant load it boosts less, so it seems that if you are getting 4.25GHz under constant load, that might actually be pretty good.

Adept II
Adept II

It says it's a 2600X in the post and it says the same in the linked spec?

Adept I
Adept I

Motherboard vendors implement different settings in their bioses according to what model motherboard.

My MSI board allows user to control XFR2 boost settings & that AMD link you listed indicates 4.2GHz boost but I'm consistently getting higher than that as measured by 2 different popular hardware monitoring apps that are regularly updated.

So unless both of those apps are wrong & MSI does not know what they are doing, then 4.2GHz is not the static ceiling for XFR2 technology for 2600X.

Journeyman III
Journeyman III

You should be glad you get those frequencies. What about me, who has a 2700X which only boosts to 4.1Ghz         (jk, I know it's important to you. And no, it's not a jk that I only get those freqs :/)

Adept I
Adept I

I was relying on HWiNFO64 for my windows app hardware monitoring before. The author of that app regularly updates it.

In using HWMONITOR it reports different boost frequencies and again, the authors update it regularly. But in saying that, keep in mind like I said before, my specific model of MSI motherboard does have fine tuning of XFR2 in it's UEFI bios options.

That just goes to show, one should not rely on just one app, even if it's reputation in the PC enthusiast's sector is held in high regard & it's updated regularly to be the sole truth of the matter...

Now if only the latest update to win 10 could fix it's specific issues, all would be fine...

Adept II
Adept II

What's really missing is an explanation of differences between XFR 1, XFR2, Precision Boost 1, Precision Boost 2, Precision Boost Overdrive and possibily XFR Enhanced. There seems to be a huge overlap.

Adept I
Adept I

MSI released 7B85v12 bios for my motherboard that includes AGESA code 1.0.0.6. After upgrading, I'm now getting regular XFR2 boosts up to 4.6GHz whilst gaming!

System is also more stable overall when under stress.

Journeyman III
Journeyman III

I'm running 2700X on MSI X470 Gaming Plus. When I'm setting PBO to Enabled and Manual Scalar to X10 it runs on 3.8 on all cores in Cinebench on 1.2v (55 C) with CB score of ~ 1680 vs 3.95-3.97 Ghz with 1.3v when PBO is set to Auto. Temps are never going after 67 C 1760 cn points. Is that expected behavior or I'm missing something?

Adept I
Adept I

Scores in cpu intensive benchmarks will be influenced by the speed of your ram with Zen+ architecture. The ring bus system is quire reliant on ram bandwidth for efficiency.

I'm running 3000MHz with 16-16-16-35 timings. It's good enough for my gaming needs atm.

Adept II
Adept II

PBO has been removed and does not work on my Asus Crosshair VI Hero