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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  • Korguz - Tuesday, July 23, 2019 - link

    sorry dude.. but YOU are uneducated, amd stays A LOT closer to its stated TDP then intel does, AT even did a review on it. power dissipated, also relates to power used. but it also doesnt help, that amd and intel both use the term TDP differently. either way.. intel uses more power then amd does.
  • Maxiking - Tuesday, July 23, 2019 - link

    Again, TDP is not power consumption and it refers to a cooler.

    You are uneducated and fabricating because you are an amd fanboy. No one really cares about what is more accurate or not, because it does not say anything about power consumption of the chip.

    So keep living in your nice little bubble. It is not my fault that you and other sites have been thinking that TDP -> power consumption. I will share something new to you again.. Ever heard about that Frankenstein novel? Frankenstein in not the monster but the doctor, his surname..Shocking I KNOW!!!

    mimimimimimi AMD good mimimimimi Intel bad
  • Korguz - Tuesday, July 23, 2019 - link

    again.. TDP, or Thermal Design Power, does relate to power consumption and how much is needed to keep something cool. You are uneducated and fabricating because you are an intel fanboy. i also notice you like to throw personal insults around when someone disagrees with you, or to try to make your opinion valid. so you keep living in your nice little bubble as well, not my fault you dont understand TDP relates to how much power something uses, as the more power a product uses, the more heat it creates, and then, needs to be removed.

    mimimimimimi intel good mimimimimi amd bad
  • Maxiking - Thursday, July 25, 2019 - link

    What you just did it is just sad. it shows you are little kid.

    TDP is not power consumption, if TDP - 100% power consumption, it would mean that 100% of the electrical energy is converted into thermal energy so yeah which is impossible it would mean perpetuum mobile you twat, actually the cpu would be net positive, it would convert 100% of electrical energy into thermal whilst managing to perform another task at no energy cost.

    Breaking the laws of physics just because of your AMD fanboyism
  • Korguz - Thursday, July 25, 2019 - link

    i said it RELATES to power consumption, what, you cant read ?? cant see passed your intel bias ?? the more power something uses, the more heat it generates, and there for, the more needs to be dissipated, and i also never said anything about 100% power consumption, pulling words and making things up to try to make your self sound right ? And you are calling me names on top of that, who's the kid here ??? Reply
  • Maxiking - Tuesday, July 23, 2019 - link

    You are uneducated, TDP doesn't mean power consumption but the amount of heat dissipated, it informs you how much of heat the cooler must be able to dissipate in order to keep the cpu cool enough to run.

    Get it? 1700x TDP was 95W yet there were tasks it managed to consume 120 or even 140w on stock settings. Like do you even watch reviews? It was the same with 2700w.

    but mimimimimimi AMD good mimimimimi Intel bad
  • Qasar - Tuesday, July 23, 2019 - link

    hmmm doest really say amd is being fraudulent, just doesnt like the idea the chips might not boost, or run at what AMD says, but didnt mention fraud...

    and Korguz has a point.. WHY arent you commenting about the power intels cpus use, vs what intel says they use ?
  • Maxiking - Tuesday, July 23, 2019 - link

    LOOOOOOL, so we have a guy confirming AMD doing fraund by misleading people about the frequency, instead of acknowledging the fraund, we gonna talk about semantics.

    Yeah, if you get sentenced for a sexual assault, you should sue then anyone who has accussed you of raping. Just wow.

    Brilliant logic, sir.
  • Maxiking - Tuesday, July 23, 2019 - link

    *fraud Reply
  • Qasar - Tuesday, July 23, 2019 - link

    still valid there buddy.. like has been said, you are the only one throwing the word fraud around, and that amd should be sued over this. so what ever Reply

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