Section by Andrei Frumusanu

The New Zen 3 Core: High-Level

As we dive into the Zen3 microarchitecture, AMD made a note of their journey of the last couple of years, a success-story that’s been started off in 2017 with the revolutionary Zen architecture that helped bring AMD back to the competitive landscape after several sombre years of ailing products.

The original Zen architecture brought a massive 52% IPC uplift thanks to a new clean-sheet microarchitecture which brought at lot of new features to the table for AMD, introducing features such as a µOP cache and SMT for the first time into the company’s designs, as well as introducing the notion of CPU core-complexes with large (8MB at the time) L3 caches. Features on a 14nm FinFET process node, it was the culmination and the start-off point of a new roadmap of microarchitectures which leads into today’s Zen3 design.

Following a minor refresh in the form of Zen+, last year’s 2019 Zen2 microarchitecture was deployed into the Ryzen 3000 products, which furthered AMD’s success in the competitive landscape. Zen2 was what AMD calls a derivative of the original Zen designs, however it contained historically more changes than what you’d expect from such a design, bringing more IPC increases than what you’d typically see. AMD saw Zen2 as a follow-up to what they had learned with the original Zen microarchitecture, fixing and rolling out design goal changes that they had initially intended for the first design, but weren’t able to deploy in time for the planned product launch window. AMD also stated that it enabled an opportunity to bring some of the future Zen3 specific changes were moved forward into the Zen2 design.

This was also the point at which AMD moved to the new chiplet design, leveraging the transition to TSMC’s new 7nm process node to increase the transistor budget for things like doubling the L3 cache size, increasing clock speeds, and vastly reducing the power consumption of the product to enable aggressive ramp in total core counts both in the consumer space (16-core Ryzen 9 3950X), as well as in the enterprise space (64-core EPYC2 Rome).

Tying a cutting-edge high-performance 7nm core-complex-die (CCD) with a lower cost 12/14nm I/O die (IOD) in such a heterogenous package allowed AMD to maximise the advantages and minimise the disadvantages of both respective technologies – all whilst AMD’s main competitor, Intel, was, and still is, struggling to bring out 10nm products to the market. It was a technological gamble that AMD many times has said was made years in advance, and has since paid off plenty.

Zen 3 At A Glance

This brings us to today’s Zen3 microarchitecture and the new Ryzen 5000 series. As noted earlier, Mark Papermaster had mentioned that if you were to actually look at the new design from a 100,000-foot level, you’d notice that it does look extremely similar to previous generation Zen microarchitectures. In truth, while Zen3 does share similarities to its predecessors, AMD’s architects started off with a clean-sheet design, or as they call it – “a ground-up redesign”. This is actually quite a large claim as this is a quite enormous endeavour to venture in for any company. Arm’s Cortex-A76 is the most recent other industry design that is said to have been designed from scratch, leveraging years of learning of the different design teams and solving inherent issues that require more invasive and large changes to the design.

Because the new Zen3 core still exhibits quite a few defining characteristics of the previous generation designs, I think that AMD’s take on a “complete redesign” is more akin to a deconstruction and reconstruction of the core’s building blocks, much like you’d dismantle a LEGO set and rebuild it anew. In this case, Zen3 seems to be a set-piece both with new building blocks, but also leveraging set pieces and RTL that they’ve used before in Zen2.

Whatever the interpretation of a “clean-sheet” or “complete redesign” might be, the important take is that Zen3 is a major overhaul in terms of its complete microarchitecture, with AMD paying attention to every piece of the puzzle and trying to bring balance to the whole resulting end-design, which comes in contrast to a more traditional “derivative design” which might only touch and see changes in a couple of the microarchitecture’s building blocks.

AMD’s main design goals for Zen3 hovered around three main points:

- Delivering another significant generational single-threaded performance increase. AMD did not want to be relegated to top performance only in scenarios where workloads would be spread across all the cores. The company wanted to catch up and be an undisputed leader in this area to be able to claim an uncontested position in the market.

- Latency improvements, both in terms of memory latency, achieved through a reduction in effective memory latency through more cache-hits thanks to the doubled 32MB L3 that an individual core can take advantage of, as well as core-to-core latency which again thanks to the consolidated single L3 cache on the die is able to reduce long travel times across the dies.

- Continuing a power efficiency leadership: Although the new Zen3 cores still use the same base N7 process node from TSMC (although with incremental design improvements), AMD had a constraint of not increasing power consumption for the platform. This means that any new performance increases would have to come through simultaneous power efficiency improvements of the microarchitecture.

The culmination of all the design changes AMD has made with the Zen3 micro-architecture results in what the company claims as a 19% average performance uplift over a variety of workloads. We’ll be breaking down this number further into the review, but internal figures show we are matching the 19% average uplift across all SPEC workloads, with a median figure of 21%. That is indeed a tremendous achievement, considering the fact that the new Ryzen 5000 chips clock slightly higher than their predecessors, further amplifying the total performance increase of the new design.

AMD Zen 3 Ryzen Deep Dive Review Zen 3: Front-End Updates & Execution Unit Redesigns
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  • 5j3rul3 - Thursday, November 5, 2020 - link

    Rip Intel🤩🤩🤩
  • Smell This - Thursday, November 5, 2020 - link

    Chipzillah has got good stuff ... everyone is "just dandy" for the most part...
    but, AMD has kicked Intel "night in the ruts" in ultimate price/performance with Zen3
  • Kangal - Saturday, November 7, 2020 - link

    True, but the price hikes really hurt.

    For the Zen3 chips, it's only worth getting the:
    - r9-5950X for the maximum best performance
    - r5-3600X for the gaming performance (and decent value).

    The 12 core r9-5900X is a complete no-buy. Whilst the r7-5800X is pretty dismal too, so both chips really need to be skipped. Neither of them have an Overclocking advantage. And there's just no gaming advantage to them over the 5600X. For more performance, get a 3950X or 5950X. And when it comes to productivity, you're better served with the Zen2 options. You can get the 3700 for much cheaper than the 5800X. Or for the same price you can get the 3900X instead.

    Otherwise, if you're looking for the ultimate value, as in something better than the 5600X value... you can look at the 3600, 1600f, 3300X, 3100 chips. They're not great for gaming/single-core tasks, but they're competent and decent at productivity. Maybe even go into the Used market for some 2700X, 2700, 1800X, 1700X, 1700, 1600X, and 1600 chips as these should be SIGNIFICANTLY cheaper. Such aggressive pricing puts these options at better value for gaming (surprising), and better value for productivity (unsurprising).
  • DazzXP - Saturday, November 7, 2020 - link

    Price hike doesn't really hurt that much, AMD was making very little money on their past Ryzen's because they had to contend with Intel Mindshare and throw more cores in as they did not quite have IPC and clock speeds, now they have all. It was as expected to be honest.
  • Silma - Sunday, November 8, 2020 - link

    Do you have any recommendations for motherboards for either a Zen3 or a Zen 2 (depending on availability of processors)? I want to spend as litte as possible on it, but it miust be compatible with 128 GB of RAM.
  • AdrianBc - Sunday, November 8, 2020 - link

    If you really intend to use 128 GB of RAM at some point in the future, you should use ECC RAM, because the risk of errors is proportional with the quantity of RAM.
    A good motherboard was ASUS Pro WS X570-ACE (which I use) previously at $300 but right now it is available at much higher prices ($370), for some weird reason.

    If you want something cheap with 128 GB and ECC support, the best you can do is an ASRock micro-ATX board with the B550 chipset. There are several models and you should compare them. For example an ASRock B550M PRO4 is USD 90 at Amazon.
  • Silma - Wednesday, November 11, 2020 - link

    Thanks for the input! Is ECC really necessary? The primary objective of the PC memory would be loading huge sound libraries in RAM for orchestral compositions. The PC would serve at the same time as gaming PC + Office PC.
  • Spunjji - Sunday, November 8, 2020 - link

    In the context of a whole system? Not really, no.

    In the context of an upgrade? Not at all, if you have a 4xx board you'll be good to go in January without having to buy a new board. That's something that hasn't been possible for Intel for a while, and won't be again until around March, when you'll be able to upgrade from a mediocre power hog of a chip to a more capable power hog of a chip.

    Comparing new to used in terms of value of a *brand new architecture* doesn't really make much sense, but go for it by all means 👍 The fact remains that these have the performance to back up the cost, which you can see in the benchmarks.
  • leexgx - Sunday, November 8, 2020 - link

    I would aim for the 5600x minimum unless your really trying to Save $100 as the 5600x is a good jump over the 3700x/3600x
  • biostud - Monday, November 9, 2020 - link

    Uhm, no? For me the 5900X would make perfect sense. I game and work with/photo video editing, and would like to have my computer for a long time. The 5950X costs too much for my needs, the 5900X offers 50% more cores than the 5800X for $100 and the 5600X hasn't got enough cores when video editing. (Although I'm waiting for next socket before upgrading my 5820k)

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