Section by Dr. Ian Cutress (Orignal article)

Windows Optimizations

One of the key points that have been a pain in the side of non-Intel processors using Windows has been the optimizations and scheduler arrangements in the operating system. We’ve seen in the past how Windows has not been kind to non-Intel microarchitecture layouts, such as AMD’s previous module design in Bulldozer, the Qualcomm hybrid CPU strategy with Windows on Snapdragon, and more recently with multi-die arrangements on Threadripper that introduce different memory latency domains into consumer computing.

Obviously AMD has a close relationship with Microsoft when it comes down to identifying a non-regular core topology with a processor, and the two companies work towards ensuring that thread and memory assignments, absent of program driven direction, attempt to make the most out of the system. With the May 10th update to Windows, some additional features have been put in place to get the most out of the upcoming Zen 2 microarchitecture and Ryzen 3000 silicon layouts.

The optimizations come on two fronts, both of which are reasonably easy to explain.

Thread Grouping

The first is thread allocation. When a processor has different ‘groups’ of CPU cores, there are different ways in which threads are allocated, all of which have pros and cons. The two extremes for thread allocation come down to thread grouping and thread expansion.

Thread grouping is where as new threads are spawned, they will be allocated onto cores directly next to cores that already have threads. This keeps the threads close together, for thread-to-thread communication, however it can create regions of high power density, especially when there are many cores on the processor but only a couple are active.

Thread expansion is where cores are placed as far away from each other as possible. In AMD’s case, this would mean a second thread spawning on a different chiplet, or a different core complex/CCX, as far away as possible. This allows the CPU to maintain high performance by not having regions of high power density, typically providing the best turbo performance across multiple threads.

The danger of thread expansion is when a program spawns two threads that end up on different sides of the CPU. In Threadripper, this could even mean that the second thread was on a part of the CPU that had a long memory latency, causing an imbalance in the potential performance between the two threads, even though the cores those threads were on would have been at the higher turbo frequency.

Because of how modern software, and in particular video games, are now spawning multiple threads rather than relying on a single thread, and those threads need to talk to each other, AMD is moving from a hybrid thread expansion technique to a thread grouping technique. This means that one CCX will fill up with threads before another CCX is even accessed. AMD believes that despite the potential for high power density within a chiplet, while the other might be inactive, is still worth it for overall performance.

For Matisse, this should afford a nice improvement for limited thread scenarios, and on the face of the technology, gaming. It will be interesting to see how much of an affect this has on the upcoming EPYC Rome CPUs or future Threadripper designs. The single benchmark AMD provided in its explanation was Rocket League at 1080p Low, which reported a +15% frame rate gain.

Clock Ramping

For any of our users familiar with our Skylake microarchitecture deep dive, you may remember that Intel introduced a new feature called Speed Shift that enabled the processor to adjust between different P-states more freely, as well as ramping from idle to load very quickly – from 100 ms to 40ms in the first version in Skylake, then down to 15 ms with Kaby Lake. It did this by handing P-state control back from the OS to the processor, which reacted based on instruction throughput and request. With Zen 2, AMD is now enabling the same feature.

AMD already has sufficiently more granularity in its frequency adjustments over Intel, allowing for 25 MHz differences rather than 100 MHz differences, however enabling a faster ramp-to-load frequency jump is going to help AMD when it comes to very burst-driven workloads, such as WebXPRT (Intel’s favorite for this sort of demonstration). According to AMD, the way that this has been implemented with Zen 2 will require BIOS updates as well as moving to the Windows May 10th update, but it will reduce frequency ramping from ~30 milliseconds on Zen to ~1-2 milliseconds on Zen 2. It should be noted that this is much faster than the numbers Intel tends to provide.

The technical name for AMD’s implementation involves CPPC2, or Collaborative Power Performance Control 2, and AMD’s metrics state that this can increase burst workloads and also application loading. AMD cites a +6% performance gain in application launch times using PCMark10’s app launch sub-test.

Hardened Security for Zen 2

Another aspect to Zen 2 is AMD’s approach to heightened security requirements of modern processors. As has been reported, a good number of the recent array of side channel exploits do not affect AMD processors, primarily because of how AMD manages its TLB buffers that have always required additional security checks before most of this became an issue. Nonetheless, for the issues to which AMD is vulnerable, it has implemented a full hardware-based security platform for them.

The change here comes for the Speculative Store Bypass, known as Spectre v4, which AMD now has additional hardware to work in conjunction with the OS or virtual memory managers such as hypervisors in order to control. AMD doesn’t expect any performance change from these updates. Newer issues such as Foreshadow and Zombieload do not affect AMD processors.

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  • PACougar - Tuesday, July 9, 2019 - link

    Lol, a boost frequency is exactly that. It doesn't mean the chips will sustain the boost for any guaranteed period of time. Do you really think it's just a coincidence that you're the only one that's "outraged" by the expected operation of these chips? Guess what, when Intel ships a chip with a stated frequency, it's also a boost with no guarantee of duration. Stock 9900k's don't run continuously at 5ghz. Lol You look like a complete fool for talking about fraud where there is none. Reply
  • Korguz - Tuesday, July 9, 2019 - link

    yea ok sure.. what ever maxiking.. you have NO idea how boost works, OR what the difference is between boost and max all core turbo is. the fact you wont post links to other sites that show this, also proves your are just trying to spread lies and BS. the only fraud i am seeing.. is you... Reply
  • Maxiking - Tuesday, July 9, 2019 - link

    We are on the side which confirms my words in the review, forums, by their tweets. Yet you are blind to the facts. Check derbauer, gaming nexus, not gonna spoonfeeding you. Reply
  • Korguz - Tuesday, July 9, 2019 - link

    let me ask you this... maxiking.. do you know the difference between boost clock. and all core turbo ? cause it sure seems you do NOT know the difference.. and others have pointed out to you that you are also wrong.. i wanted links.. to be sure i am looking at the same sites as you.. in the end.. you are just trolling.. and talking bs... drop this already.. Reply
  • Qasar - Wednesday, July 10, 2019 - link

    Check derbauer, gaming nexus... never heard of these sites.. i can see why Korguz is asking you to post links directly to where you are getting this, and i agree, BS from... Reply
  • Maxiking - Tuesday, July 9, 2019 - link

    There is a debate going about this on every internet forum, so no I am not the only one concerned and the AMD subreddit has a dedicated thread about it as well.

    If Intel ships a chip with any stated boost frequency, the boosts are guaranteed on the per core usage basis. Stock 9900k runs at 5.0 ghz, the more cores are being used, the lower frequency..a single core always run @ 5.0ghz, all cores @ 4.7ghz. I already said it earlier. Sorry my friend, wrong example, the only fool here is you.

    The fact is that Ryzen 3rd gen is a worse overclocker than the 2nd one. Or you know, I will give AMD the benefit of doubt. Before the reviews were up, the whole internet had been going crazy and thinking that 4.6 on all cores was possible, because "look at those boost frequency man". And that was the AMD intention. To use those sporadical 100 - 200ms spikes to spread the idea that the final product would able to reach them on all cores, to misguide. And I must say it WORKED brilliantly, ADOREDTV is now the biggest clown on the internet, easy 5ghz+, he said. I wonder if he makes ConLake style videos about this.

    So yeah, that 4.6ghz boost is fraud. The majority can't reach it on a single core and the rest capable of doing so only by performing non frequent 100 - 200ms long spikes.

    If Intel did this, oh god, what a shitstorm would be here, just like with their TDP, Meltdown, Spectre. Every review would be full of this. Don't blame me, I am just pointing at facts and making fun of petty suddenly blind amd fans. Don't shoot the messenger.
    Reply
  • Korguz - Tuesday, July 9, 2019 - link

    well.. 1st.. you didnt answer my question if you know the difference between boost clock and all core turbo.. 2nd.. you are the only one on here.. that is crying about this.. define every internet forum... also.. you do not seem to replying to any one else in this thread about this.. Reply
  • Targon - Monday, July 22, 2019 - link

    I've seen 4.4GHz without doing any BIOS tweaking on a 3900X on an Asus ROG Crosshair VI Hero. BIOS is still AGESA 1.0.0.2, so I haven't bothered to even try pushing to 4.6GHz yet. I wouldn't say that a boost to 4.6GHz with a good BIOS version isn't possible based on what I have seen with X370, and expecting that X570 has a good chance to be better about how to handle the new chips.

    As far as Intel and boost speeds, that is based as well on cooling. You try a 95W TDP rated cooler, and you will NOT be hitting anywhere close to 5.0GHz boost. You would need something significant. That 95W TDP is a fraud, because it only applies to base speeds, while the AMD TDP figures are in line with what most people will hit.
    Reply
  • kd_ - Tuesday, July 9, 2019 - link

    Take it easy, Bob Reply
  • Irata - Tuesday, July 9, 2019 - link

    Did you bother to read Andrei F's twitter post regarding the Bios update - it includes a nice graph where you can see the 3900x's cores boosting to what looks like 4.6 Ghz. Reply

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