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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  • YukaKun - Saturday, April 21, 2018 - link

    Oh, I'm actually curious about your experience with all the systems.

    I'm still running my i7 2700K at ~4.6Ghz. I do agree I haven't felt that it's a ~2012 CPU and it does everything pretty damn well still, but I'd like to know if you have noticed a difference between the new AMD and your Sandy Bridge. Same for when you assemble the 2700X.

    I'm trying to find an excuse to get the 2700X, but I just can't find one, haha.

    Cheers!
    Reply
  • Luckz - Monday, April 23, 2018 - link

    The the once in a lifetime chance to largely keep your CPU name (2700K => 2700X) should be all the excuse you need. Reply
  • YukaKun - Monday, April 23, 2018 - link

    That is so incredibly superficial and dumb... I love it!

    Cheers!
    Reply
  • mapesdhs - Monday, April 23, 2018 - link

    YukaKun, your 2700K is only at 4.6? Deary me, should be 5.0 and proud, doable with just a basic TRUE and one fan. 8) For reference btw, a 2700K at 5GHz gives the same threaded performance as a 6700K at stock.

    And I made a typo in my earlier reply, mentioned the wrong XEON model, should have been the 2680 V2.
    Reply
  • YukaKun - Tuesday, April 24, 2018 - link

    For daily usage and stability, I found that 4.6Ghz worked best in terms of noise/heat/power ratios.

    I also did not disable any power saving features, so it does not work unnecessarily when not under heavy load.

    I'm using AS5 with a TT Frio (the original one) on top, so it's whisper quiet at 4.6Ghz and I like it like that. When I made it work at 5Ghz, I found I had to have the fans near 100%, so it wasn't something I'd like, TBH.

    But, all of this to say: yes, I've done it, but settled with 4.6Ghz.

    Cheers!
    Reply
  • mapesdhs - Friday, March 29, 2019 - link

    (an old thread, but in case someone comes across it...)

    I use dynamic vcore so I still get the clock/voltage drops when idle. I'm using a Corsair H80 with 2x NDS 120mm PWM, so also quiet even at full load; no need for such OTT cooling to handle the load heat, but using an H80 means one can have low noise aswell. An ironic advantage of the lower thermal density of the older process sizes. Modern CPUs with the same TDP dump it out in a smaller area, making it more difficult to keep cool.

    Having said that, I've been recently pondering an upgrade to have much better general idle power draw and a decent bump for threaded performance. Considering a Ryzem 5 2600 or 7 2700, but might wait for Zen2, not sure yet.
    Reply
  • moozooh - Sunday, April 22, 2018 - link

    No, it might have to do with the fact that the 8350K has 1.5x the cache size and beastly per-thread performance that is also sustained at all times—so it doesn't have to switch from a lower-powered state (which the older CPUs were slower at), nor does it taper off as other cores get loaded, which is most noticeable on the the things Samus mentioned, ie. "boot times, app launches and gaming". Boot times and app launches are both essentially single-thread tasks with no prior context, and gaming is where a CPU upgrade like that will improve worst-case scenarios by at least an order of magnitude, which is really what's most noticeable.

    For instance, if your monitor is 60Hz and your average framerate is 70, you won't notice the difference between 60 and 70—you will only notice the time spent under 60. Even a mildly overclocked 8350K is still the one of best gaming CPUs for this reason, easily rivaling or outperforming previous-gen Ryzens in most cases and often being on par with the much more expensive 8700K where thread count isn't as important as per-thread performance for responsiveness and eliminating stutters. When pushed to or above 5 GHz, I'm reasonably certain it will still give many of the newer, more expensive chips, a run for their money.
    Reply
  • spdragoo - Friday, April 20, 2018 - link

    Memory prices? Memory prices are still pretty much the way they've always been:
    -- faster memory costs (a little) more than slower memory
    -- larger memory sticks/kits cost (a little) more than smaller sticks/kits
    -- last-gen RAM (DDR3) is (very slightly) cheaper than current-gen RAM (DDR4)

    I suppose you can wait 5 billion years for the Sun to fade out, at which point all RAM (or whatever has replaced it by then) will have the same cost ($0...since no one will be around to buy or sell it)...but I don't think you need to worry about that.
    Reply
  • Ferrari_Freak - Friday, April 20, 2018 - link

    You didn't write anything about price there... All you've said is that relative pricing for things is the same it has always been, and that's no surprise.

    The $$$ cost of any give stick is more than it was a year or two ago. 2x8gb DDR4-3200 G.Skill Ripjaws V is $180 on Newegg today. It was $80 two years ago. Clearly not the way they've always been...
    Reply
  • James5mith - Friday, April 20, 2018 - link

    2x16GB Crucial DDR4-2400 SO-DIMM kit.

    https://www.amazon.com/gp/product/B019FRCV9G/

    November 29th 2016 (when I purchased): $172

    Current Amazon price for exact same kit: $329
    Reply

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