Last week, we published our AMD 2nd Gen Ryzen Deep Dive, covering our testing and analysis of the latest generation of processors to come out from AMD. Highlights of the new products included better cache latencies, faster memory support, an increase in IPC, an overall performance gain over the first generation products, new power management methods for turbo frequencies, and very competitive pricing.

In our review, we had a change in some of the testing. The big differences in our testing for this review was two-fold: the jump from Windows 10 Pro RS2 to Windows 10 Pro RS3, and the inclusion of the Spectre and Meltdown patches to mitigate the potential security issues. These patches are still being rolled out by motherboard manufacturers, with the latest platforms being first in that queue. For our review, we tested the new processors with the latest OS updates and microcode updates, as well as re-testing the Intel Coffee Lake processors as well. Due to time restrictions, the older Ryzen 1000-series results were used.

Due to the tight deadline of our testing and results, we pushed both our CPU and gaming tests live without as much formal analysis as we typically like to do. All the parts were competitive, however it quickly became clear that some of our results were not aligned with those from other media. Initially we were under the impression that this was as a result of the Spectre and Meltdown (or Smeltdown) updates, as we were one of the few media outlets to go back and perform retesting under the new standard.

Nonetheless, we decided to take an extensive internal audit of our testing to ensure that our results were accurate and completely reproducible. Or, failing that, understanding why our results differed. No stone was left un-turned: hardware, software, firmware, tweaks, and code. As a result of that process we believe we have found the reason for our testing being so different from the results of others, and interestingly it opened a sizable can of worms we were not expecting.


An extract from our Power testing script

What our testing identified is that the source of the issue is actually down to timers. Windows uses timers for many things, such as synchronization or ensuring linearity, and there are sets of software relating to monitoring and overclocking that require the timer with the most granularity - specifically they often require the High Precision Event Timer (HPET). HPET is very important, especially when it comes to determining if 'one second' of PC time is the equivalent to 'one second' of real-world time - the way that Windows 8 and Windows 10 implements their timing strategy, compared to Windows 7, means that in rare circumstances the system time can be liable to clock shift over time. This is often highly dependent on how the motherboard manufacturer implements certain settings. HPET is a motherboard-level timer that, as the name implies, offers a very high level of timer precision beyond what other PC timers can provide, and can mitigate this issue. This timer has been shipping in PCs for over a decade, and under normal circumstances it should not be anything but a boon to Windows.

However, it sadly appears that reality diverges from theory – sometimes extensively so – and that our CPU benchmarks for the Ryzen 2000-series review were caught in the middle. Instead of being a benefit to testing, what our investigation found is that when HPET is forced as the sole system timer, it can  sometimes a hindrance to system performance, particularly gaming performance. Worse, because HPET is implemented differently on different platforms, the actual impact of enabling it isn't even consistent across vendors. Meaning that the effects of using HPET can vary from system to system, as well as the implementation.

And that brings us to the state HPET, our Ryzen 2000-series review, and CPU benchmarking in general. As we'll cover in the next few pages, HPET plays a very necessary and often very beneficial role in system timer accuracy; a role important enough that it's not desirable to completely disable HPET – and indeed in many systems this isn't even possible – all the while certain classes of software such as overclocking & monitoring software may even require it. However for a few different reasons it can also be a drain on system performance, and as a result HPET shouldn't always be used. So let's dive into the subject of hardware timers, precision, Smeltdown, and how it all came together to make a perfect storm of volatility for our Ryzen 2000-series review.

A Timely Re-Discovery
POST A COMMENT

242 Comments

View All Comments

  • andrewaggb - Thursday, April 26, 2018 - link

    that MS link was very informative. Thanks Reply
  • chrcoluk - Wednesday, April 25, 2018 - link

    So the question is, What other things in the OS have you "tweaked" and not disclosed? Reply
  • peevee - Thursday, April 26, 2018 - link

    This. Reply
  • Krysto - Wednesday, April 25, 2018 - link

    Windows just release 2 new Spectre mitigations - make sure to include those, too. Reply
  • mode_13h - Thursday, April 26, 2018 - link

    Any success replicating these results with their new BIOS/AGESA? Or is that a Linux-only fix?

    https://www.phoronix.com/scan.php?page=article&...
    Reply
  • GreenReaper - Friday, April 27, 2018 - link

    It may also cause a significant improvement in Raven Ridge performance:
    https://overclock3d.net/news/cpu_mainboard/agesa_v...
    Reply
  • takeshi7 - Wednesday, April 25, 2018 - link

    How do I check and/or change the OS-level HPET setting in Windows?
    I'd like to know if my system is in the forced-HPET mode.
    Reply
  • Alistair - Wednesday, April 25, 2018 - link

    run cmd prompt as an administrator
    bcdedit /enum
    if there is a line like "use platformclock on" , then it is forced on
    if no line, then it is off
    BIOS is a "off" / "available" toggle, so there is no "on" in bios
    Reply
  • JoeyJoJo123 - Wednesday, April 25, 2018 - link

    I'm probably misinterpreting this, and feel free to correct me, but initial read of the title would suggest to the common user that "AMD Ryzen 2 has an issue with its internal timer", but upon reading, not only does Ryzen 2's HPET have a minimal performance hit compared to default behavior, but Intel's _own_ HPET is the variant with the LARGEST performance penalty.

    This information would imply that the Ryzen 2 benchmarks done so far only stand to gain a bit of performance (under default configurations), but nothing more than ~15% on very select game titles at 1080p, and less than ~5% elsewhere. (This is a good thing, as the good Ryzen 2 benchmarks only stand to gain a bit by measuring performance with HPET off.) It also then implies that Intel should likely be reviewing their HPET implementation to ensure that there's a minimal performance hit for applications which use this feature.
    Reply
  • Ryan Smith - Wednesday, April 25, 2018 - link

    "I'm probably misinterpreting this, and feel free to correct me, but initial read of the title would suggest to the common user that "AMD Ryzen 2 has an issue with its internal timer", but upon reading, not only does Ryzen 2's HPET have a minimal performance hit compared to default behavior, but Intel's _own_ HPET is the variant with the LARGEST performance penalty."

    Ultimately this article was a follow-up to our Ryzen 2 review, so it was necessary that it referenced it. (However the use of an Intel CPU picture was also very intentional)
    Reply

Log in

Don't have an account? Sign up now