A Timely Discovery: Examining Our AMD 2nd Gen Ryzen Results
by Ian Cutress & Ryan Smith on April 25, 2018 11:15 AM ESTAMD 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.
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bbertram - Wednesday, April 25, 2018 - link
Well this is interesting! This could have serious implications.Googled HPET really quick and found this: https://www.reddit.com/r/Planetside/comments/416ns...
and then I found this link from that thread....a little ironic.
https://forums.anandtech.com/threads/do-you-have-h...
bbertram - Wednesday, April 25, 2018 - link
An interesting article that talks more about the issue. They look to even have a benchmark to show the impact. The video is also very interesting. The more I research this problem the more i see its been know for a very long time now.https://tinyurl.com/yd8qsh7w
bbertram - Wednesday, April 25, 2018 - link
ohhh...more nice info: https://tinyurl.com/yd39zw8c_mat - Wednesday, April 25, 2018 - link
Very thorough article. I like to point out a few things though, that may add some information to this.AMD and especially Intel have swept this problem under the rug since the launch of Skylake X. I noticed this problem while benching for a review and initially thought that my OS installation was the cause. After some testing I finally found the same root of evil as Ian did. At that time I made a video and called it the "Intel X299 HPET" bug (can't post a link, it was already mentioned in the comments here).
I tried to talk to PR and engineers at Intel for quite a while and they heard about my bug report but refused to comment. Time went by and Threadripper and Coffee Lake were born, both inheriting the same slow HPET QPC timer calls. I informed Intel repeatedly, still no comment.
During that time I wrote the following benchmark that sheds some light on the whole QPC and timer business on Windows. It shows your Windows timer configuration, gives recommendations for precision and performance, provides a way to bench your QPC timer in a synthetic and a game test and gives easy access to change TSC to HPET and vice versa.
As I am not able to post a link here, please search for "TimerBench", you will be able to download it.
I am also the author of GPUPI, one of those benchmarks for overclockers mentioned in the article that enforced HPET timers for secure timing a while back. Since discovering the HPET bug I have pulled back on this restriction. Since Skylake HPET is no longer necessary to avoid BCLK skewing, iTSC is just fine. AMD is still affected though, possibly Ryzen 2 as well (Threadripper and Ryzen 1 was).
bbertram - Wednesday, April 25, 2018 - link
Link to download: https://tinyurl.com/y7w6tg36Link to article: https://tinyurl.com/yd8qsh7w
Arbie - Thursday, April 26, 2018 - link
Wow! Google translator is amazing when going from German to English!mapesdhs - Sunday, May 6, 2018 - link
Might be because English has its roots in Germanic languages. :D Old English sounds a lot like common words in Dutch, and there's a region in Germany where the way German is spoken can sound to other Germans to be rather like English (according to a German guy I know). It's all those pesky Saxons, Angles, etc. :DTrackSmart - Wednesday, April 25, 2018 - link
Thank you _mat! Hopefully your comment gets attention here at Anandtech, and in turn, this article and your work get some attention from Intel. On the AMD side, it sounds like enabling HPET has only a small penalty in most cases, but those differences on the Intel side are very troubling. At the very least we should be forewarned!Dark_wizzie - Wednesday, April 25, 2018 - link
What software causes HPET to be forced on in Windows? I have multiple software installed but it still appears off.Dec666 - Wednesday, April 25, 2018 - link
Hi, AT.First of all, I wanted to thank you for an extreme effort you put in your reviews and analysis.
My thinking on the subject is that if you disable HPET in OS, this may make your numbers and review conclusion be irrelevant to the real world scenarios. As you have said, many programs (like video streaming, monitoring/overclocking, and potentially motherboard software (not to say about Ryzen Master)) require HPET to be enabled in OS and they will force it during the installation process and most likely won’t inform you about this. That means, that if you’ve installed all the software you going to use on fresh OS (and/or fresh PC), it is very possible that some of that software will have HPET forced and you won’t know about it.
To my mind, most of people, who read CPU reviews, are enthusiasts and/or those, who want to make a decision on CPU purchase by themselves. The majority of people will just buy PC based on others’ opinion or consultant’s advise. So those, for whom 10% difference in performance matters, and/or those, who bought expensive GPU like 1080/1080ti, will probably use monitoring software like HWinfo or Afterburner. That means, that HPET will be forced on their systems. That means, that they will have real world numbers close to what you’ve got in the original Ryzen 2000 review.
Another thing is that by disabling HPET in OS, while doing tests for a new review, you will hide the problem with it on Intel systems. People will not consider this as a potential performance hit or disadvantage of Intel platform in general.
Moreover, I suspect that in future more programs and, probably, next-gen games will require HPET (in order to better synchronize even more threads). Since most of people buy CPU for more than one year, they will have potentially worse experience with Intel CPUs in future, compared to AMD CPUs.
So it looks more logical to me to test CPUs with HPET forced (for all software), but have additional tests with HPET disabled for just games in order to have games tested with HPET both on and off. That will emphasize the problem. For me this is the same reason why it is important to test hardware with all Smeltdown patches and BIOS updates installed.
Thanks.