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
Comments Locked


View All Comments

  • mapesdhs - Sunday, May 6, 2018 - link

    Have you monitored your CPU usage and I/O behaviour? Just wondering if an NVMe SSD would help, assuming you don't already have one.
  • agilesmile - Wednesday, April 25, 2018 - link

    I can't understand why you portray HPET as a magical highest precision timer? TSC is faster and more accurate when it has proper implementation (modern CPUs).
    Would be really useful to test how overclocking modern CPUs affect TSC and maybe report bugs to the CPU manufacturers if it still does.

    FYI here's more about TSC and HPET:
  • Senti - Wednesday, April 25, 2018 - link

    TSC isn't only the highest resolution timer – it's also the cheapest one in terms of latency.
    It has only 2 major problems:
    1) On some really old CPUs it's tied to actual CPU clock and changes according to frequency change.
    2) It's tied to system base clock and changes with it.

    But since base clock overclocking is dead you can pretty much consider TSC as a stable timer now.
  • Billy Tallis - Wednesday, April 25, 2018 - link

    There's also the inconvenience that the TSC is a per-core timer, and it's hard to get the TSCs exactly synchronized between cores, so software that needs really high resolution timing also needs to worry about thread pinning.
  • BillyONeal - Wednesday, April 25, 2018 - link

    Not to mention cross socket and power management impacts!
  • Billy Tallis - Thursday, April 26, 2018 - link

    The power management effects were fixed way back with Nehalem. With even desktop CPUs doing clock speed changes all the time (eg. Turbo Boost), TSC would be useless if it didn't account for any of that. Nowadays, the TSC is only vulnerable to distortion from unusual sources of clock speed changes, like BCLK overclocking or drift in the clock generator.
  • Senti - Wednesday, April 25, 2018 - link

    Plenty of words and nothing about another solution of timing problems: drop always-in-beta Win10 and test on stable Win7.

    You write that you care about 'gamers' and 'default configuration' and ignore that Win7 share is almost 2x the Win10 one (according to Steam). In enterprise there is even less love for Win10.
  • BillyONeal - Wednesday, April 25, 2018 - link

    That's awfully hard given that Win7 isn't supported on Ryzen.
  • SkyBill40 - Friday, April 27, 2018 - link

    *DING, DING!*
  • mapesdhs - Sunday, May 6, 2018 - link

    Plenty of mbd vendors support Win7 with Ryzen, whatever the official support is supposed to be. Most mbd vendors are not so dumb as to lock out the largest share of the market.

Log in

Don't have an account? Sign up now