Precision Boost 2 and XFR2: Ensuring It Hertz More

One of the biggest changes for the new Ryzen-2000 series is in how the processor implements its turbo. Up until this point (except the recent APU launch), processors have relied on a step function implementation: the system determines how many threads are loaded, attempts to implement a specific frequency on those cores if possible, and then follows the look-up table relating thread count to frequency. AMD’s goal in Precision Boost 2 is to make this process more dynamic.

This image from AMD is how the feature is being represented: the system will determine how much of the power budget is still available, and turbo as much as possible until it hits one of the limiting factors. These factors can be any of, but not limited to, the following:

  1. Total chip peak power
  2. Individual core voltage/frequency response
  3. Thermal interactions between neighboring cores
  4. Power delivery limitations to individual cores/groups of cores
  5. Overall thermal performance

AMD’s new Ryzen Master 1.3 software, when used on a Ryzen 2000-series processor, has several indicators to determine what the limiting factors are. For the most part, the way the processor will boost and respond to the environment, will be transparent to the user.

The best way to test this in action, from my perspective, is to look at the power draw of the first generation and second generation Ryzen processors. We can examine the internal estimated power consumption of each core individually as thankfully AMD has left these registers exposed, to give the following data:

This is only the core consumption power, not the package power, which would include the DRAM controller, the Infinity Fabric, and the processor IO. This means we get numbers different to the rated TDP, but the danger here is that because the Ryzen 7 2700X has a 10W TDP higher than the Ryzen 7 1800X, where the 2700X draws more power it could seem as if that is the TDP response.

Just plotting the power consumption gives this graph:

Even in this case it is clear that the Ryzen 7 2700X is drawing more power, up to 20W more, for a variable threaded load. If we change the graph to be a function of peak power:

The results are not quite as clear: it would seem that the 1800X draws, as a percentage of peak power, more at low thread count, but the 2700X draws more at a middling thread count.

It is worth noting that the end result of Precision Boost 2 is two-fold: more performance, but also more power consumption. Users looking to place one of the lower powered processors into a small form factor system might look at disabling this feature and returning to a standard step-function response in order to keep the thermal capabilities in check.

A side note – despite the marketing name being called ‘Precision Boost 2’, the internal BIOS name is called ‘Core Performance Boost’. It sounds similar to Multi-Core Enhancement, which is a feature on some Intel motherboards designed to go above and beyond the turbo mechanism. However, this is just AMD’s standard PB2: disabling it will disable PB2. Initially we turned it off, thinking it was a motherboard manufacturer tool, only to throw away some testing because there is this odd disconnect between AMD’s engineers and AMD’s marketing.

Extended Frequency Range 2 (XFR2)

For the Ryzen 2000-series, AMD has changed what XFR does. In the previous generation it was applied on certain processors to allow them to boost above the maximum turbo frequency when the thermal situation was conducive to higher frequencies and higher voltage in low thread-count states. For this generation, it still relates to thermals, however the definition is applied to any core loading: if the CPU is under 60ºC, the processor can boost no matter what the loading is above its Precision Boost 2 frequency (so why not get a better PB2 implementation?). The core still has to be within a suitable voltage/frequency window to retain stability, however.

On certain motherboards, like the ASUS Crosshair VII Hero, there are additional options to assist XFR2 beyond AMD’s implementation. ASUS does not go into specific details, however I suspect it implements a more aggressive version, perhaps extending the voltage/frequency curve, raising the power limits, and/or adjusting the thermal limit.

 

 

 

Translating to IPC: All This for 3%? New X470 Chipset and Motherboards: A Focus on Power
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  • jjj - Thursday, April 19, 2018 - link

    I was wondering about gaming, so there is no mistake there as Ryzen 2 seems to top Intel.
    As of right now, I don't seem to find memory specs in the review yet, safe to assume you did as always, highest non-OC so Ryzen is using faster DRAM?
    Also yet to spot memory letency, any chance you have some numbers at 3600MHz vs Intel? Thanks.
    Reply
  • jjj - Thursday, April 19, 2018 - link

    And just between us, would be nice to have some Vega gaming results under DX12. Reply
  • aliquis - Thursday, April 19, 2018 - link

    Would be nice if any reviewer actually benchmarked storage devices maybe even virtualization because then we'd see meltdown and spectre mitigation performance. Then again do AMD have any for spectre v2 yet? If not who knows what that will do. Reply
  • HStewart - Thursday, April 19, 2018 - link

    I notice that that systems had higher memory, but for me I believe single threaded performance is more important that more cores. But it would be bias if one platform is OC more than another. Personally I don't over clock - except for what is provided with CPU like Turbo mode.

    One thing that I foresee in the future is Intel coming out with 8 core Coffee Lake

    But at least it appears one thing is over is this Meltdown/Spectre stuff
    Reply
  • Lolimaster - Thursday, April 19, 2018 - link

    Intel 8 core CL won't stop the bleeding, lose more profits making them "cheap" vs a new Ryzen 7nm with at least 10% more clocks and 10% more IPC, RIP. Reply
  • HStewart - Thursday, April 19, 2018 - link

    I just have to agree to disagree on that statement - especially on "cheap" statement Reply
  • ACE76 - Thursday, April 19, 2018 - link

    CL can't scale to 8 cores...not without done serious changes to it's architecture...Intel is in some trouble with this Ryzen refresh...also worth noting is that 7nm Ryzen 2 will likely bring a considerable performance jump while Intel isn't sitting on anything worthwhile at the moment. Reply
  • Alphasoldier - Friday, April 20, 2018 - link

    All Intel's 8cores in HEDT except SkylakeX are based on their year older architecture with a bigger cache and the quad channel.

    So if Intel have the need, they will simply make a CL 8core. 2700X is pretty hungry when OC'd, so Intel don't have to worry at all about its power consuption.
    Reply
  • moozooh - Sunday, April 22, 2018 - link

    > 2700X is pretty hungry when OC'd
    And Intel chips aren't? If Zen+ is already on Intel's heels for both performance per watt and raw frequency, a 7nm chip with improved IPC and/or cache is very likely going to have them pull ahead by a significant margin. And even if it won't, it's still going to eat into Intel's profit as their next tech is 10nm vs. AMD's 7nm, meaning more optimal wafer estate utilization for the latter.

    AMD has really climbed back at the top of their game; I've been in the Intel camp for the last 12 years or so, but the recent developments throw me way back to K7 and A64 days. Almost makes me sad that I won't have any reason to move to a different mobo in the next 6–8 years or so.
    Reply
  • mapesdhs - Friday, March 29, 2019 - link

    Amusing to look back given how things panned out. So yes, Intel released the 9900K, but it was 100% more expensive than the 2700X. :D A complete joke. And meanwhile tech reviewers raved about a peasly 5 to 5.2 oc, on a chip that already has a 4.7 max turbo (major yawn fest), focusing on specific 1080p gaming tests that gave silly high fps number favoured by a market segment that is a tiny minority. Then what happens, RTX comes out and pushes the PR focus right back down to 60Hz. :D

    I wish people to stop drinking the Intel/NVIDIA coolaid. AMD does it aswell sometimes, but it's bizarre how uncritical tech reviewers often are about these things. The 9900K dragged mainstream CPU pricing up to HEDT levels; epic fail. Some said oh but it's great for poorly optimised apps like Premiere, completely ignoring the "poorly optimised" part (ie. why the lack of pressure to make Adobe write better code? It's weird to justify an overpriced CPU on the back of a pro app that ought to run a lot better on far cheaper products).
    Reply

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