The AMD ‘Zen 2’ Micro Architecture – All You Need To Know

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AMD’s next generation “Zen 2” core which was largely a mystery up until earlier in the month when the company revealed details of its 7nm Zen 2 microarchitecture, which represents the second and perhaps most significant step in the Zen timeline, which dates back to 2017 with the launch of its first generation Ryzen, Ryzen Threadripper, and EPYC CPUs..

AMD’s representative Mark Papermaster said that the new 7nm Zen 2  core is in partnership with TMSC, which will be manufacturing it. From the outset, he says a doubling of core density and halving of power consumption for the same performance, both potentially indicating that we’ll see increased core counts in future from its CPUs. He also said that Zen 2 will offer a 1.2x performance boost in IPC over current Zen+-based CPUs helped along by using a second generation Infinity Fabric.

Zen 2, despite its name, is actually going to power the company’s 3rd generation lineup of Ryzen processors and here is a list of some key enhancements coming with “Zen 2”

  • Improved Execution Pipeline
  • Doubled Floating Point (256-bit) and Load/Store (Doubled Bandwidth)
  • Doubled Core Density
  • Half the Energy Per Operation
  • Improved Branch Prediction
  • Better Instruction Pre-Fetching
  • Re-Optimized Instruction Cache
  • Larger Op Cache
  • Increased Dispatch / Retire Bandwidth
  • Maintaining High Throughput for All Modes

And now, thanks to a leak on the Sisoft Sandra database via TPU, we can also add double the L3 cache to that list. An entry for an upcoming ROME processor featuring the company’s Zen 2 core has popped up and it revealed that the 64 core chip actually features a whopping 256MB of L3 cache. That’s 16 MB per CCX, double that of the previous generation.

A larger L3 means that the system would have to fetch data from DDR4 memory less often, which translates to faster work completion at less power which contributes in IPC and power efficiency benefits that Zen 2 brings with itself in comparison to original Zen design.

Image by eTeknix

Zen 2 will be the building block of its Ryzen and Ryzen Threadripper desktop CPUs as well as its EPYC server CPUs and is the most significant step in Zen’s timeline for a number of reasons. AMD needs to keep driving performance upwards to stay competitive and already made significant gains with Zen+, offering higher frequencies and improved boosting algorithms that offered tangible benefits, especially in lightly-threaded workloads. The move to 7nm should allow for higher frequencies as well as increased yields and this will impact all three tiers of its current processor line-up.

Along with the new 7nm process node, AMD is taken a modular approach, still using some 14nm silicon in the design to keep costs down and yields high. This new approach will allow the company to double the core density of the architecture, which could potentially mean 16-core chips hitting our desktops. Quite what we’d do with those extra cores in our gaming rigs, I don’t really know, but it would comfortably increase both the core-count and process node lead over Intel.

AMD isn’t stopping there, with the Zen 3 design already in the pipe, and ‘on track’ for a release sometime in 2020 on the 7nm+ node. So, if Zen 2 only has a year to live what can the next-gen architecture offer to make it a must-have processor for our gaming rigs?

As AMD has confirmed, it has already started sampling out processors using the Zen 2 CPU architecture. That means there are early engineering samples out in the wild, and the first noises we’ve heard about a desktop-based version has come from a September post on HardOCP’s forum claiming knowledge of a chip sent to AMD Radeon Technology Group.

This chip is reportedly an eight-core, 16-thread Zen 2 CPU with a base clock speed of 4GHz and a boost frequency of 4.5GHz. Considering the top Zen+ processor of the second-gen Ryzen range, the Ryzen 7 2700X, has the base and boost clocks of 3.7GHz and 4.3GHz respectively that’s an impressive start for an early engineering sample.

The first Zen engineering samples ran at 2.8GHz and 3.2GHz for its base and boost frequencies, before hitting our desktops as the 3.6GHz / 4GHz Ryzen 7 1800X. The fact that AMD is getting early silicon out of the fab and into the hands of testers and it’s running at speeds already faster than today’s best Ryzen 7 processor bodes well for the first Zen 2 launch chips.

Given the 7nm lithography used in the CPU chipsets of Zen 2 it’s not a stretch to believe that AMD will be looking to produce final silicon that’s capable of even higher clock speeds. If it can match Intel’s 5GHz boost then the tables really could turn, with AMD potentially offering both more cores and higher performance.

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