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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  • Marlin1975 - Thursday, April 19, 2018 - link

    Looks good, guess AMD will replace my Intel system next.

    Just waiting for GPU and memory prices to fall.
    Reply
  • 3DoubleD - Thursday, April 19, 2018 - link

    Agreed... the waiting continues Reply
  • WorldWithoutMadness - Thursday, April 19, 2018 - link

    Lol, you might even wait until Zen 2 comes out next year or even later. Reply
  • Dragonstongue - Thursday, April 26, 2018 - link

    should be out next year as AMD has been very much on the ball with Ryzen launches more or less to the DAY they claimed would launch which is very nice...basically what they are promising for product delivery they are doing what they say IMO, not to mention TSMC recently announced volume production of their 7nm, so that likely means GloFo will be very soon to follow, and AMD can use TSMC just the same :) Reply
  • t.s - Tuesday, July 31, 2018 - link

    What @WWM want to say is: You can wait forever for the RAM price to go down, rather than when ryzen 2 out. Reply
  • StevoLincolnite - Thursday, April 19, 2018 - link

    I still haven't felt limited by my old 3930K yet.

    Can't wait to see what Zen 2 brings and how Intel counters that.
    Reply
  • mapesdhs - Friday, April 20, 2018 - link

    If you ever do fancy a bit more oomph in the meantime (and assuming IPC is less important than threaded performance, eg. HandBrake is more important than PDF loading), a decent temporary sideways step for X79 is a XEON E5-2697 v2 (IB-EP). An oc'd 3930K is quicker for single-threaded of course, but for multithreaded the XEON does very well, easily beating an oc'd 3930K, and the XEON has native PCIe 3.0 so no need to bother with the not entirely stable forced NVIDIA tool. See my results (for FireFox, set Page Style to No Style in the View menu):

    http://www.sgidepot.co.uk/misc/tests-jj.txt
    Reply
  • mapesdhs - Monday, April 23, 2018 - link

    Correction, I meant the 2680 v2. Reply
  • Samus - Friday, April 20, 2018 - link

    I never felt limited by my i5-4670k either, especially mildly overclocked to 4.0GHz.

    Until I build a new PC around the same old components because the MSI Z97 motherboard (thanks MSI) failed (it was 4 years old but still...) so I picked up a new i3-8350k + ASRock Z270 at Microcenter bundled together for $200 a month ago, and it's a joke how much faster it is than my old i5.

    First off, it's noticeably faster, at STOCK, than the max stable overclock I could get on my old i5. Granted I replaced the RAM too, but still 16GB, now PC4-2400 instead of PC3-2133. Doubt it makes a huge difference.

    Where things are noticeably faster comes down to boot times, app launches and gaming. All of this is on the same Intel SSD730 480GB SATA3 I've had for years. I didn't even do a fresh install, I just dropped it in and let Windows 10 rebuild the HAL, and reactivated with my product key.

    Even on paper, the 8th gen i3's are faster than previous gen i5's. The i3 stock is still faster than the 4th gen i5 mildly overclocked.

    I wish I waited. It's compelling (although more expensive) to build an AMD Ryzen 2 now. It really wasn't before, but now that performance is slightly better and prices are slightly lower, it would be worth the gamble.
    Reply
  • gglaw - Saturday, April 21, 2018 - link

    i think there's something wrong with your old Haswell setup if the difference is that noticeable. I have every generation of Intel I7 or I5 except Coffee Lake running in 2 rooms attached to each other, and I can't even notice a significant difference from my SANDY 2600k system with a SATA 850 Evo Pro sitting literally right next to my Kaby I7 with a 960 EVO NVMe SSD. I want to convince myself how much better the newer one is, but it just isn't. And this is 5 generations apart for the CPU's/mobos and using one of the fastest SSD's ever made compared to a SATA drive, although about the fastest SATA drive there is. Coffee Lake is faster than Kaby but so tiny between the equivalent I7 to I7, I can't see myself noticing a major difference.

    In the same room across from these 2 is my first Ryzen build, the 1800X also with an 960 EVO SSD. Again, I can barely convince myself it's a different system than the Sandy 2600k with SATA SSD. I have your exact Haswell I5 too, and it feels fast as hell still. Especially for app launches and gaming. The only time I notice major differences between these systems is when I'm encoding videos or running synthetic benchmarks. Just for the thrill of a new flagship release I just ordered the 2700X too and it'll be sitting next to the 1800X for another side by side experience. It'll be fun to setup but I'm pretty convinced I won't be able to tell the 2 systems apart when not benchmarking.

    Reply

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