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.
Facebook
Twitter
RSS
242 Comments
View All Comments
bbertram - Thursday, April 26, 2018 - link
I think you will see alot of websites testing these combinations and re-validating their results. How do we trust any benchmarks now? Going to be some fun reading in the coming weeks.Ryan Smith - Thursday, April 26, 2018 - link
"Please take this comment into account when deciding if you're going to be flipping HEPT switches with every game on both CPU brands."Thankfully, we have no need to flip any switches for HPET. The new testing protocol is that we're sticking with the default OS settings. Which means HPET is available to the OS, but the system isn't forced to use it over all other timers.
"And hey, I didn't see it, but did you do any comparisons on if GPU maker makes a difference to the HEPT impact on CPU maker?" We've done a couple of tests internally. Right now it doesn't look like it makes a difference. Not that we'd expect it to. The impact of HPET is to the CPU.
HeyYou,It'sMe - Thursday, April 26, 2018 - link
Even before the patches, using the HPET timer causes severe system overhead. This is a known issue that is exacerbated slightly by the patches, but there isn't a massive increase in overhead. AnandTech should post HPET overhead before and after the patches. You will find the impact is much the same.eva02langley - Thursday, April 26, 2018 - link
Also, HPET seems to have a higher impact on old games. Maybe it was the way older engine were developed.Also, are we sure HPET is not just messing with the FPS data since the timing could be off?
peevee - Thursday, April 26, 2018 - link
Great illustration of the phrase that "it's better not to know than know something which isn't so".Standard 1kHz RTC is good enough for all real performance measurement where measured tasks run for at least a second or two (otherwise such performance just does not matter in the PC context). Multiple measurement, plus elimination of false precision from averaging the results would eliminate all errors significant for the task.
When you have to change default system configuration to run the tests, the tests reflect these non-default configurations nobody is running at home or at work, and as such simply irrelevant.
pogostick - Thursday, April 26, 2018 - link
I don't understand how using HPET on Intel could have such a drastic effect. Just the fact that it is available slows the system down? How? A benchmark only needs to access this timer once at the beginning and once at the end. There is no need for incessant polling of the clock. Is the only way to guarantee that you are using it to force it on for the whole system? What do these differences look like in other OSes? There are way too many questions unanswered here.Is it not more likely that using non-HPET timers allows the platform to essentially create it's own definition for what constitutes "1 second"? Wouldn't using a timer based on the core tend to stretch out the definition of "1 second" over a longer period if the core becomes heavily taxed or heated?
These systems need to be tested with a common clock. Whether that is some specialized pcie device, or a network clock, or a new motherboard standard that offers special pins to an external clock source, or whatever, is to be determined elsewhere. All boards need to be using the same clock for testing.
Ryan Smith - Thursday, April 26, 2018 - link
I don't understand how using HPET on Intel could have such a drastic effect. Just the fact that it is available slows the system down?It's not that it's available is the problem. The issue is that the OS is forced to use it for all timer calls.
"How?"
Relative to the other timers, such as QPC, HPET is a very, very expensive timer to check. It requires going to the OS kernel and the kernel in turn going to the chipset, which is quite slow and time-consuming compared to any other timer check.
"A benchmark only needs to access this timer once at the beginning and once at the end. There is no need for incessant polling of the clock."
Games have internal physics simulations and such. Which require a timer to see how much time has elapsed since the last step of the simulation. So the timer can actually end up being checked quite frequently.
"Is the only way to guarantee that you are using it to force it on for the whole system?"
As a user, generally speaking: yes. Otherwise a program will use the timer the developer has programmed it to use.
"Wouldn't using a timer based on the core tend to stretch out the definition of "1 second" over a longer period if the core becomes heavily taxed or heated?"
No. Modern Invariant timers are very good about keeping accurate time, and are very cheap to access.
pogostick - Friday, April 27, 2018 - link
Thank you.risa2000 - Monday, April 30, 2018 - link
"Games have internal physics simulations and such. Which require a timer to see how much time has elapsed since the last step of the simulation. So the timer can actually end up being checked quite frequently."Would it be too difficult to set up a profiler session and count how many times is HPET called and eventually even from where?
To produce such an impact it must be a load of calls and I still cannot imagine why so many.
Next, why Intel suffers so much by forced HPET compared to new AMD?
Kaihekoa - Friday, April 27, 2018 - link
Excuses excuses.