AMD and Intel Have Different HPET Guidance

A standard modern machine, with a default BIOS and a fresh Windows operating system, will sit on the first situation in the table listed above: the BIOS has HPET enabled, however it is not explicitly forced in the operating system. If a user sets up their machine with no overclocking or monitoring software, which is the majority case, then this is the implementation you would expect for a desktop.

AMD

We reached out to AMD and Intel about their guidance on HPET, because in the past it has both been unclear as well as it has been changed. We also reached out to motherboard manufacturers for their input.

For those that remember the Ryzen 7 1000-series launch, about a year ago from now, one point that was lightly mentioned among the media was that in AMD’s press decks, it was recommended that for best performance, HPET should be disabled in the BIOS. Specifically it was stated that:

Make sure the system has Windows High Precision Event Timer (HPET) disabled. HPET can often be disabled in the BIOS. [T]his can improve performance by 5-8%.

The reasons at the time were unclear as to why, but it was a minor part in the big story of the Zen launch so it was not discussed in detail. However, by the Ryzen 5 1000-series launch, that suggestion was no longer part of the reviewer guide. By the time we hit the Ryzen-2000 series launched last week, the option to adjust HPET in the BIOS was not even in the motherboards we were testing. We cycled back to AMD about this, and they gave the following:

The short of it is that we resolved the issues that caused a performance difference between on/off. Now that there is no need to disable HPET, there is no need for a toggle [in the BIOS].

Interestingly enough, with our ASUS X470 motherboard, we did eventually find the setting for HPET – it was not in any of the drop down menus, but it could be found using their rather nice ‘search’ function. I probed ASUS about whether the option was enabled in the BIOS by default, given that these options were not immediately visible, and was told:

It's enabled and never disabled, since the OS will ignore it by default. But if you enable it, then the OS will use it – it’s always enabled, that way if its needed it is there, as there would be no point in pulling it otherwise.

So from an AMD/ASUS perspective, the BIOS is now going to always be enabled, and it needs to be forced in the OS to be used, however the previous guidance about disabling it in the BIOS has now gone, as AMD expects performance parity.

It is worth noting that AMD’s tool, Ryzen Master, requires a system restart when the user first loads it up. This is because Ryzen Master, the overclocking and monitoring tool, requires HPET to be forced in order to do what it needs to do. In fact, back at the Ryzen 7 launch in 2017, we were told:

AMD Ryzen Master’s accurate measurements present require HPET. Therefore it is important to disable HPET if you already installed and used Ryzen Master prior to game benchmarking.

Ultimately if any AMD user has Ryzen Master installed and has been run at any point, HPET is enabled, even if the software is not running or uninstalled. The only way to stop it being forced in the OS is with a command to chance the value in the BCD, as noted above.

For the Ryzen 2000-series launch last week, Ryzen Master still requires HPET to be enabled to run as intended. So with the new guidance that HPET should have minimal effect on benchmarks, the previous guidance no longer applies.

Ryzen Master is not the only piece of software that requires HPET to be forced in order to do what it needs to do. For any of our readers that have used overclocking software and tools before, or even monitoring tools such as fan speed adjusters – if those tools have requested a restart before being used properly, there is a good chance that in that reboot the command has been run to enable HPET. Unfortunately it is not easy to generate a list, as commands and methods may change from version to version, but it can apply to CPU and GPU overclocking.

Intel

The response we had from Intel was a little cryptic:

[The engineers recommend that] as far as benchmarking is concerned, it should not matter whether or not HPET is enabled or not. There may be some applications that may not function as advertised if HPET is disabled, so to be safe, keep it enabled, across all platforms. Whatever you decide, be consistent across platforms.

A cold reading of this reply would seem to suggest that Intel is recommended HPET to be forced and enabled, however my gut told me that Intel might have confused ‘on’ in the BIOS with ‘forced’ through the OS, and I have asked them to confirm.

Looking back at our coverage of Intel platforms overall, HPET has not been mentioned to any sizeable degree. I had two emails back in 2013 from a single motherboard manufacturer stating that disabling HPET in the BIOS can minimise DPC latency on their motherboard, however no comment was made about general performance. I cannot find anything explicitly from Intel though.

A Timely Re-Discovery Forcing HPET On, Plus Spectre and Meltdown Patches
Comments Locked

242 Comments

View All Comments

  • tiwake - Wednesday, April 25, 2018 - link

    Phoronix reports that there is an update AGESA 1.0.0.2a for the ASUS X470 motherboard he has that brings another 6% performance increase with seemingly everything on linux and the ryzen 7 2700X.
  • Alexvrb - Wednesday, April 25, 2018 - link

    "however the most gains were limited to specific titles at the smaller resolutions, which would be important for any user relying on fast frame rates at lower resolutions."

    Uhh, isn't that negated by more stuttering without HPET? Or does having it "available" provide the same real-world smooth gameplay as having it forced on, but somehow also boost benchmarks?
  • Ryan Smith - Thursday, April 26, 2018 - link

    You shouldn't seeing stuttering in normal scenarios. If anythng, it's forcing the use of HPET that could lead to stuttering, since it's a relatively expensive system call to make.
  • tmiller02 - Wednesday, April 25, 2018 - link

    So... now this has me thinking... which results are accurate. Are the new findings used by intel to show an artificial boost on benchmarks... I just cant grasp this much of a performance difference just by hpet bsing forced on... it seems to be just the reporting is skewed.... which sounds very pro intel!
  • Ryan Smith - Thursday, April 26, 2018 - link

    As amazing as it looks, the new results are accurate. Forcing the use of HPET really does have a sizable performance impact in some of these games. Particularly, I suspect, any game that likes to call on OS for timers a lot.
  • TheNerd389 - Thursday, April 26, 2018 - link

    While I know that running your tests without HPET forced is most representative for most people, would it be unreasonable to ask that the results with HPET forced be presented moving forward?

    For instance, I use HPET timer for collecting performance data for software that I write. If enabling HPET can cause a 10-30% drop in performance, it makes a huge difference to me. That's enough of a difference to throw off the measurements of parallel fine-grained operations by a very substantial margin. In my case, that would result in improperly tuned code.

    Based on your results with Ryzen 2, there is a much more significant difference between the 2700X and the 8700K than most reviews suggest for my application. That's an important insight from my perspective. If the pattern holds for the HEDT chips or, *shudder*, Epyc and Xeon, there is a lot to lose by not considering the effects of HPET. In those spaces, it could mean missing out on several thousand dollars worth of performance per CPU by choosing the wrong architecture.
  • Billy Tallis - Thursday, April 26, 2018 - link

    This issue shouldn't matter at all in the server space, because one of the only reasons to force the HPET to be used as the primary timer is to get accurate timing when overclocking (or get results at stock speed that can be fairly compared against accurate overclocked results). Servers don't get overclocked, so they can rely on the TSC for most of their timing needs and not have to incur the HPET overhead on every time check. (The HPET will still get used for some things, but it doesn't have to be the only time source when the TSC is trustworthy.)
  • bbertram - Thursday, April 26, 2018 - link

    The problem is just not for overclocked CPUs. Also what if you don't know if HPET is being forced? Who knows to check for that? What software can force it on?
  • TheNerd389 - Thursday, April 26, 2018 - link

    Have you considered build farms and/or testing farms that gather performance data? Those are what I'm referring to here.
  • bairlangga - Thursday, April 26, 2018 - link

    Is there really no adverse effects on defaulting to not forcing HPET? Imho, calculation is not always on accuracy but also on the timely manner. In measurement, benchmarking, or maybe in controlling it would matter a lot. On the other hand in gaming I don't know if it's correct understanding but it could cause untimely frames, or part of it, ghosting, or artefacts, etc.

    Found an interesting article:
    http://hexus.net/tech/news/cpu/103531-amd-tech-gur...

Log in

Don't have an account? Sign up now