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
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  • eddman - Friday, April 27, 2018 - link

    No, TSC in modern CPUs is constant.
  • gammaray - Wednesday, April 25, 2018 - link

    could you run tests in 1440p? thx.
  • brxndxn - Wednesday, April 25, 2018 - link

    Seriously.. 1080p sucks.
  • crimson117 - Thursday, April 26, 2018 - link

    They run in both 1080p and 1440p.

    When you are examine CPU performance, 1440p is usually bottlenecked by the GPU, so the CPUs are all waiting around for the GPU and don't get to really show who's faster.

    When you run at 1080p, the GPU has no problem handling that, so CPUs are no longer waiting around for the GPU. More responsive CPU's keep up with the GPU to provide super high framerates. Slower CPUs will drag the system down, lowering framerates especially in CPU-intensive situations like tracking lots of players or mobs at once.
  • chrcoluk - Wednesday, April 25, 2018 - link

    You didnt ask the most important people, Microsoft the developers of Windows. They state the default timers shouldnt be fiffled with unless you are debugging timer problems or have a specific need to force a certian timer. TSC is the best performing timer for modern processors.

    I remember a couple of years back when I followed a silly guide on the net to force HPET in windows and later discovered it was the blame for weird stutters I had in games.

    If AMD's own software is forcing HPET in the OS and especially they not telling the end user what they doing then thats very irresponsible.
  • ReverendCatch - Wednesday, April 25, 2018 - link

    On the other hand, everything was 1% difference, which is barely even academic.

    Tomb Raider seems to be an outlier on both platforms.
  • Alistair - Wednesday, April 25, 2018 - link

    Yes I'd like to see AMD change their software to avoid using HPET. It shouldn't be doing so.
  • Evil Underlord - Wednesday, April 25, 2018 - link

    "both companies seem to be satisfied when HPET is enabled in the BIOS and irreverent when HPET is forced in the OS"

    God save us from irreverent chip manufacturers.
  • mildewman - Wednesday, April 25, 2018 - link

    A really interesting article. I disabled HPET at motherboard level a few months ago in the pursuit of lower usb latency, and noticed it also made game framerates slightly smoother. (i5 3470, Z77 chipset, win10 x64)
  • unbellum - Wednesday, April 25, 2018 - link

    I would love to see your results and hear your thoughts with regard to the compilation benchmark. As a developer fighting long build times, this is extremely relevant to my current work.

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