Many AMD Ryzen 3000 CPUs Don’t Hit Full Boost Clock: Report

 

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Overclocker Der8auer has published the results of a survey of more than 3,000 Ryzen 7nm owners who have purchased AMD’s new CPUs since they went on sale in July. Last month, reports surfaced that the Ryzen 3000 family weren’t hitting their boost clocks as well as some enthusiasts expected. Now, we have some data on exactly what those figures look like.

There are, however, two confounding variables. First, Der8auer had no way to sort out which AMD users had installed Windows 1903 and were using the most recent version of the company’s chipset drivers. AMD recommends both to ensure maximum performance and desired boost behavior. Der8auer acknowledges this but believes the onus is on AMD to communicate with end-users regarding the need to use certain Windows versions to achieve maximum performance.

Second, there’s the fact that surveys like this tend to be self-selecting. It’s possible that only the subset of end-users who aren’t seeing the performance they desire will respond in such a survey. Der8auer acknowledges this as well, calling it a very valid point, but believes that his overall viewing community is generally pro-AMD and favorably inclined towards the smaller CPU manufacturer. The full video can be seen below; we’ve excerpted some of the graphs for discussion.

 

Der8auer went over the data from the survey thoroughly in order to throw out results that didn’t make sense or were obviously submitted in bad faith. He compiled data on the 3600, 3600X, 3700X, 3800X, and 3900X.SEEAMAZON_ET_135 See Amazon ET commerce Clock distributions were measured at up to two deviations from the mean. Maximum boost clock was tested using Cinebench R15’s single-threaded test, as per AMD’s recommendation.

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Data and chart by Der8auer. Click to enlarge

In the case of the Ryzen 7 3600, 49.8 percent of CPUs hit their boost clock of 4.2GHz, as shown above. As clocks rise, however, the number of CPUs that can hit their boost clock drops. Just 9.8 percent of 3600X CPUs hit their 4.4GHz. The 3700X’s chart is shown below for comparison:

Data and chart by Der8auer. Click to enlarge

The majority of 3700X CPUs are capable of hitting 4.375GHz, but the 4.4GHz boost clock is a tougher leap. The 3800X does improve on these figures, with 26.7 percent of CPUs hitting boost clock. This seems to mirror what we’ve heard from other sources, which have implied that the 3800X is a better overclocker than the 3700X. The 3900X struggles more, however, with just 5.6 percent of CPUs hitting their full boost clock.

We can assume that at least some of the people who participated in this study did not have Windows 10 1903 or updated AMD drivers installed, but AMD users had the most reason to install those updates in the first place, which should help limit the impact of the confounding variable.

The Ambiguous Meaning of ‘Up To’

Following his analysis of the results, Der8auer makes it clear that he still recommends AMD’s 7nm Ryzen CPUs with comments like “I absolutely recommend buying these CPUs.” There’s no ambiguity in his statements and none in our performance review. AMD’s 7nm Ryzen CPUs are excellent. But an excellent product can still have issues that need to be discussed. So let’s talk about CPU clocks.

The entire reason that Intel (who debuted the capability) launched Turbo Boost as a product feature was to give itself leeway when it came to CPU clocks. At first, CPUs with “Turbo Boost” simply appeared to treat the higher, optional frequency as their effective target frequency even when under 100 percent load. This is no longer true, for multiple reasons. CPUs from AMD and Intel will sometimes run at lower clocks depending on the mix of AVX instructions. Top-end CPUs like the Core i9-9900K may throttle back substantially when under full load for a sustained period of time (20-30 seconds) if the motherboard is configured to use Intel default power settings.

In other realms, like smartphones, it is not necessarily unusual for a device to never run at maximum clock. Smartphone vendors don’t advertise base clocks at all and don’t provide any information about sustained SoC clock under load. Oftentimes it is left to reviewers to typify device behavior based on post-launch analysis. But CPUs from both Intel and AMD have typically been viewed as at least theoretically being willing capable of hitting boost clock in some circumstances.

The reason I say that view is “theoretical” is that we see a lot of variation in CPU behavior, even over the course of a single review cycle. It’s common for UEFI updates to arrive after our testing has already begun. Oftentimes, those updated UEFIs specifically fix issues with clocking. We correspond with various motherboard manufacturers to tell them what we’ve observed and we update platforms throughout the review to make certain power behavior is appropriate and that boards are working as intended. When checking overall performance, however, we tend to compare benchmark results against manufacturer expectations as opposed to strictly focusing on clock speed (performance, after all, is what we are attempting to measure). If performance is oddly low or high, CPU and RAM clocks are the first place to check.

It’s not unusual, however, to be plus-or-minus 2-3 percent relative to either the manufacturer or our fellow reviewers, and occasional excursions of 5-7 percent may not be extraordinary if the benchmark is known for producing a wider spread of scores. Some tests are also more sensitive than others to RAM timing, SSD speed, or a host of other factors.

Now, consider Der8auer’s data on the Ryzen 9 3900X:

Der8auer-3900X

Image and data by Der8auer. Click to enlarge

Just 5 percent of the CPUs in the batch are capable of hitting 4.6GHz. But a CPU clocked at 4.6GHz is just 2 percent faster than a CPU clocking in at 4.5GHz. A 2 percent gap between two products is close enough that we call it an effective tie. If you were to evaluate CPUs strictly on the basis of performance, with a reasonable margin of say, 3 percent, you’d wind up with an “acceptable” clock range of 4,462MHz – 4,738MHz (assuming a 1:1 relationship between CPU clock and performance). And if you allow for that variance in the graphs above, a significantly larger percentage — though no, not all — of AMD CPUs “qualify” as effectively reaching their top clock.

On the other hand, 4.5GHz or below is factually not 4.6GHz. There are at least two meaningfully different ways to interpret the meaning of “up to” in this context. Does “up to X.XGHz” mean that the CPU will hit its boost clock some of the time, under certain circumstances? Or does it mean that certain CPUs will be able to hit these boost frequencies, but that you won’t know if you have one or not? And how much does that distinction matter, if the overall performance of the part matches the expected performance that the end-user will receive?

Keep in mind that one thing these results don’t tell us is what overall performance looks like across the entire spread of Ryzen 7 CPUs. Simply knowing the highest boost clock that the CPU hits doesn’t show us how long it sustained that clock. A CPU that holds a steady clock of 4.5GHz from start to finish will outperform a CPU that bursts to 4.6GHz for one second and drops to 4.4GHz to finish the workload. Both of these behaviors are possible under an “up to” model.

Manufacturers and Consumers May See This Issue Differently

While I don’t want to rain on his parade or upcoming article, we’ve spent the last few weeks at ET troubleshooting a laptop that my colleague David Cardinal recently bought. Specifically, we’ve been trying to understand its behavior under load when both the CPU and GPU are simultaneously in-use. Without giving anything away about that upcoming story, let me say this: The process has been a journey into just how complicated thermal management is now between various components.

Manufacturers, I think, increasingly look at power consumption and clock speed as a balancing act in which performance and power are allocated to the components where they’re needed and throttled back everywhere else. Increased variability is the order of the day. What I suspect AMD has done, in this case, is set a performance standard that it expects its CPUs to deliver rather than a specific clock frequency target. If I had to guess at why the company has done this, I would guess that it’s because of the intrinsic difficulties of maintaining high clock speeds at lower process nodes. AMD likely chose to push the envelope on its clock targets because it made the CPUs compare better against their Intel equivalents as far as maximum clock speeds were concerned. Any negative response from critics would be muted by the fact that these new CPUs deliver marked benefits over both previous-generation Ryzen CPUs and their Intel equivalents at equal price points.

Was that the right call? I’m not sure. This is a situation where I genuinely see both sides of the issue. The Ryzen 3000 family delivers excellent performance. But even after allowing for variation caused by Windows version, driver updates, or UEFI issues on the part of the manufacturer, we don’t see as many AMD CPUs hitting their maximum boost clocks as we would expect, and the higher-end CPUs with higher boost clocks have more issues than lower-end chips with lower clocks. AMD’s claims of getting more frequency out of TSMC 7nm as compared with GF 12/14nm seem a bit suspect at this point. The company absolutely delivered the performance gains we wanted, and the power improvements on the X470 chipset are also very good, but the clocking situation was not detailed the way it should have been at launch.

There are rumors that AMD supposedly changed boost behavior with recent AGESA versions. Asus employee Shamino wrote:

i have not tested a newer version of AGESA that changes the current state of 1003 boost, not even 1004. if i do know of changes, i will specifically state this. They were being too aggressive with the boost previously, the current boost behavior is more in line with their confidence in long term reliability and i have not heard of any changes to this stance, tho i have heard of a ‘more customizable’ version in the future.

I have no specific knowledge of this situation, but this would surprise me. First, reliability models are typically hammered out long before production. Companies don’t make major changes post-launch save in exceptional circumstances, because there is no way to ensure that the updated firmware will reach the products that it needs to reach. When this happens, it’s major news. Remember when AMD had a TLB bug in Phenom? Second, AMD’s use of Adaptive Frequency and Voltage Scaling is specifically designed to adjust the CPU voltage internally to ensure clock targets are hit, limiting the impact of variability and keeping the CPU inside the sweet spot for clock.

I’m not saying that AMD would never make an adjustment to AGESA that impacted clocking. But the idea that the company discovered a critical reliability issue that required it to make a subtle change that reduced clock by a mere handful of MHz in order to protect long-term reliability doesn’t immediately square with my understanding of how CPUs are designed, binned and tested. We have reached out to AMD for additional information.

I’m still confident and comfortable recommending the Ryzen 3000 family because I’ve spent a significant amount of time with these chips and seen how fast they are. But AMD’s “up to” boost clocks are also more tenuous than we initially knew. It doesn’t change our expectation of the part’s overall performance, but the company appears to have decided to interpret “up to” differently this cycle than in previous product launches. That shift should have been communicated. Going forward, we will examine both Intel and AMD clock behavior more closely as a component of our review coverage.

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