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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After so many decades and with so many transistors available can't Intel/AMD add better more efficient and accurate ways of getting time (e.g. monotonic time and also "real time")? They keep adding YetAnotherSIMD but how about stuff like this? For bonus points add efficient easy ways to set (and cancel) interrupts that will trigger after certain times.patrickjp93 - Monday, April 30, 2018 - link
It's a total misconception that any circuit can get these times more accurately and efficiently at the same time. There's no demand for it on a broad scale either.Bensam123 - Saturday, April 28, 2018 - link
This has been something the gaming community has known about and discussed for years, you can find posts about HPET all over popular forums. However, they aren't backed by any sort of meaningful data and much like with core parking and vpns for gaming, legitimate hardware testing websites generally have either turned up their nose at it or disregarded them as complete snake oil.I'm glad HPET is finally getting looked at in real depth. What was discussed here was just their real effect on quantifiable metrics, such as benchmarks, but what gamers discuss is their impact on stuttering or microstutters as well as hit registration in netcode (which is extremely dependent on timing). That wasn't looked at at all here. While this discussion was mainly focused on the difference between results between other websites and Intel vs AMD, I think that's not quite the right way to approach this. Rather it should be looked at the effect of timers in general on gaming as a whole.
The statement that you guys received from Intel pretty much makes it blatantly clear that no one really had any idea what was going on with the timers over there or that they really had a big impact on anything outside of synthetic results. Microsoft has just put band aids on top of band aids to keep everything running and it got to the point where it's no longer transparent to people who are buying hardware, people who are making hardware, or people who are developing software (beyond a few very niche groups) how they all interlock and intermingle with each other. I didn't until I did some digging and required even more to learn there were more timers besides HPET between multiple and sometimes vaguely related forum posts.
A higher resolution timer should be good, especially for video games, but the impact it has on the system because of it's crude and backwards implementation has made it such that it's basically just a synthetic cog that can't be used in practice. It makes you wish there was a solution that just put everything on the same page, hardware and software. I'm sure game developers who just lease a engine and then essentially make a mod have no idea what's going on here and developers who actually make the engine (Dice, Epic, Crytek) may not even know there is a problem in the first place.
I do hope Anand takes this a bit further with frame time benchmarks and maybe FCAT designed to look specifically at this. As was mentioned in this article, implementations even seem different across different motherboards, which is a very, very bad thing and should also be looked at. There is a lot of room for future articles here focused around this specific issue until there is some remote amount of standardization.
If you're looking for more interesting things to test - almost no one tests net code in video games, with the handful of people who do making arbitrary comparisons and really having no tools or benchmarks to work with, even though video games (especially highly competitive ones) are extremely dependent on such things, especially when you get into the top 10% of the player base. People just assume gaming code 'works' and that magical part of games are all created equal when it couldn't be any further from the truth. Net code is literally trying to hold together what is essentially a train wreck while trying to mask it from it's users as best as possible. Some games do it a lot better then others.