Core-to-Core, Cache Latency, Ramp

For some of our standard tests, we look at how the CPU performs in a series of synthetic workloads to example any microarchitectural changes or differences. This includes our core-to-core latency test, a cache latency sweep across the memory space, and a ramp test to see how quick a system runs from idle to load.

Core-to-Core

Inside the chip are eight cores connected through a bi-directional ring, each direction capable of transmitting 32 bytes per cycle. In this test we test how long it takes to probe an L3 cache line from a different core on the chip and return the result.

For two threads on the same core, we’re seeing a 7 nanosecond difference, whereas for two separate cores we’re seeing a latency from 15.5 nanoseconds up to 21.2 nanoseconds, which is a wide gap. Finding out exactly how much each jump takes is a bit tricky, as the overall time is reliant on the frequency of the core, of the cache, and of the fabric over the time of the test. It also doesn’t tell us if there is anything else on the ring aside from the cores, as there is also going to be some form of external connectivity to other elements of the SoC.

However, compared to the Zen3 numbers we saw on the Ryzen 9 5980HS, they are practically the same.

Cache Latency Ramp

This test showcases the access latency at all the points in the cache hierarchy for a single core. We start at 2 KiB, and probe the latency all the way through to 256 MB, which for most CPUs sits inside the DRAM.

Part of this test helps us understand the range of latencies for accessing a given level of cache, but also the transition between the cache levels gives insight into how different parts of the cache microarchitecture work, such as TLBs. As CPU microarchitects look at interesting and novel ways to design caches upon caches inside caches, this basic test proves to be very valuable.

The data here again mirrors exactly what we saw with the previous generation on Zen3.

Frequency Ramp

Both AMD and Intel over the past few years have introduced features to their processors that speed up the time from when a CPU moves from idle into a high-powered state. The effect of this means that users can get peak performance quicker, but the biggest knock-on effect for this is with battery life in mobile devices, especially if a system can turbo up quick and turbo down quick, ensuring that it stays in the lowest and most efficient power state for as long as possible.

Intel’s technology is called SpeedShift, although SpeedShift was not enabled until Skylake.

One of the issues though with this technology is that sometimes the adjustments in frequency can be so fast, software cannot detect them. If the frequency is changing on the order of microseconds, but your software is only probing frequency in milliseconds (or seconds), then quick changes will be missed. Not only that, as an observer probing the frequency, you could be affecting the actual turbo performance. When the CPU is changing frequency, it essentially has to pause all compute while it aligns the frequency rate of the whole core.

We wrote an extensive review analysis piece on this, called ‘Reaching for Turbo: Aligning Perception with AMD’s Frequency Metrics’, due to an issue where users were not observing the peak turbo speeds for AMD’s processors.

We got around the issue by making the frequency probing the workload causing the turbo. The software is able to detect frequency adjustments on a microsecond scale, so we can see how well a system can get to those boost frequencies. Our Frequency Ramp tool has already been in use in a number of reviews.

A ramp time of within one millisecond is as expected for modern AMD platforms, although we didn’t see the high 4.9 GHz that AMD has listed this processor as being able to obtain. We saw it hit that frequency in a number of tests, but not this one. AMD’s previous generation took a couple of milliseconds to hit around the 4.0 GHz mark, but then another 16 milliseconds to go full speed. We didn’t see it in this test, perhaps due to some of the new measurements AMD is doing on core workload and power. We will have to try this on a different AMD Ryzen 6000 Mobile system to see if we get the same result.

AMD's Ryzen 9 6900HS Rembrandt Benchmarked Power Consumption
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  • Kangal - Sunday, March 6, 2022 - link

    Zeno, Guards of Zeno, Grand Priest, Whis/Angels, Awakened Gass, Ultra Granolah, Ultra Instinct Goku, Beerus/GoDs, Fused Zamasu, Prime Moro, Raged Broly, Ultra Ego Vegeta, Full-power Jiren, LSS Kefla, Destruction Toppo, Max Hit, Anilaza, SSJ Rose Black, Golden Frieza, Dyspo, LSS Kale, Spirit Future Trunks, Super Ribrianne, Trained #17, Ultimate Gohan, Buu, Seven-Three.
    Reply
  • GeoffreyA - Monday, March 7, 2022 - link

    Astonishing, and thanks for that! Remembering only Buu, Ultimate Gohan, and a bit of Beerus, I am really out of touch with DB canon! Reply
  • Kangal - Tuesday, March 8, 2022 - link

    You can find the new series Dragon Ball Super online or even youtube. There is also the official manga which you can read for free* here:
    https://www.viz.com/shonenjump/chapters/dragon-bal...

    *only the latest three issues available, new issues always free.
    Reply
  • GeoffreyA - Tuesday, March 8, 2022 - link

    Thanks, I only saw the first 10-15 episodes of Super in 2018, where Beerus came to the cruiseship, and still hope to watch the rest of it, eventually. It was nostalgic, I remember, seeing these dear characters after so long. Reply
  • mode_13h - Wednesday, March 9, 2022 - link

    Eh, I only watched the original series. The few things after it that I had seen lacked the same charm. And among that series, the first season was one of the best. The censors had clearly cracked down on it, after that.

    What I thought worked so well about the original DB was Goku's innocence, ignorance, indomitable spirit, and purity of heart. That made it so much more entertaining and gratifying to see him overcome all the obstacles and enemies he encountered. And it's almost as if not knowing his own limitations made him unrestrained by them.
    Reply
  • GeoffreyA - Thursday, March 10, 2022 - link

    That's an exact description of Goku's character and is likely the secret of his greatness and why he often prevailed over his enemies. I would add that forgiveness was another trait of his, and something they could never understand. It's almost paradoxical, at least in DBZ, how he was the comic clumsy figure, and yet when it came to saving the world, only he could do it. Without knowing it, people are emulating, I feel, more of Vegeta's cynical character today. What the world needs is more of Goku. Reply
  • mode_13h - Friday, March 11, 2022 - link

    I haven't watched much since the mid 2000's, but I thought Luffy, in One Piece, had a similar personality. However, he seemed to have a mercurial wisdom and canniness, just beneath the surface. In that regard, he seemed to have echos of Irresponsible Captain Taylor.

    I don't remember too much of Naruto, though I had started watching it from the beginning. Like Goku, he also had an innocence and indomitably, but there was obviously a darkness about him and inside of him.

    I wouldn't have patience for any of that, now. Even at the time, it seemed rather excessively drawn out.

    BTW, did you see the live action DB movie? I think it was made around 2008? More of a Hollywood movie; not Japanese. I'm apparently among the small minority who actually liked it. It helps to remember that Dragon Ball itself is loosely based on the ancient tale of Saiyuki and just don't expect a direct translation from the TV series or manga. It's very much a reinterpretation, but I enjoyed it.
    Reply
  • GeoffreyA - Monday, March 14, 2022 - link

    Luffy is very like Goku, regarding his innocence, simplicity, and goodness, but yes, he had another element which is hard to pin down. Perhaps a certain stoic quality that clicked on at times, and made him something fearful to all those who practised evil. (It's even evident when they left the Merry; Goku would never have operated like that, and for my part, I agree with Usopp.) I really loved One Piece. It could often be tedious and silly, but once the story knocked into gear, it was usually astonishing, and gave you the feeling of being on an adventure with noble companions. Namaka. My favourite arcs were Arlong/Nami, Arabasta, and Water 7. In 2018, I got stuck at Thriller Bark and never went on.

    What caused me to stop was seeing Evangelion for the first time that year. It left me a sadder, more sober person for ever; and I'll add a word of warning to others, Eva is terribly depressing and no joke. That and Steins;Gate are my favourite anime. I've heard great things about Naruto but to this day have not seen a single episode. Rurouni Kenshin was nice.

    My brother really enjoyed the live-action Dragon Ball, but though I've seen only bits and pieces, I always debate with him that it's not the real DB! He contends that it's pretty good. Well, perhaps I need to sit down and actually watch it and give it a proper appraisal.
    Reply
  • mode_13h - Tuesday, March 15, 2022 - link

    Wow, all those One Piece names are definitely a flashback. I hung out with some Kenshin fans, so I saw the entire original series.

    Evangelion was pretty mind-blowing for me, when the original series first aired. A bit confusing, especially with the movies, the revisionist ending, and whatnot.

    More recently, I went to a marathon showing of the original series, back when they started releasing the new version. I watched the first 2-3 installments of the new version and just quit. It got too absurd for me. I never liked the direction Gainax took with FLCL, but I guess it was inevitable the new Eva would go there (and lose me). I did really like Kare Kano and Chobits (lol, they seemed to have HDDs inside!).

    I got a lot from Evangelion, but I'm pretty much over it. Not unlike how I parted ways with the Star Wars franchise, more than a decade ago. I just don't need it. I don't seem to have trouble finding enough to watch. For instance, a movie I recently enjoyed was Arrival.

    Even the news is like a high-tension drama, for at least the past half decade. I can really feel like I'm living through history. It gives me a new perspective on much of the past century and what it was probably like, at the time.

    Some other old anime that's fun to re-watch are the original Patlabor OAV series and movies, Akira, and the Ghost in the Shell series and movies. And every time I hear about space junk in the news, my mind goes back to Planetes.
    Reply
  • GeoffreyA - Tuesday, March 15, 2022 - link

    Evangelion is indeed out of this world. It's really the sadness of the characters that touched me, though of course the relentless, minimal action was impressive when it came. Can anyone ever forget Eva-01 breaking out of the shadow space in episode 16, or the time, nearing the end, when it reactivates though its power is gone? The new movies' weakness is that they tried to spin everything out to excessive detail, whereas the series' strength was minimalism. The characterisation, too, was subtly altered. Anyhow, last year I watched the final film, Thrice upon a Time, and can honestly say they did a good job and ended Eva on a surprisingly cheerful note, with a good message. I secretly hope for a return someday.

    I haven't seen most of the anime you mentioned, except for Akira and Ghost in the Shell. Suffice to say, Akira leaves the viewer speechless.

    Same here. Lost my interest in Star Wars and don't care to see it again. Arrival was great, with a good performance by Amy Adams. And talking of Villeneuve movies, the new Dune was a big disappointment to me.
    Reply

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