We're only two weeks away from Ryzen's half a decade long awaited arrival. This is the AMD CPUthat PC hardware enthusiasts have eagerly looked forward to for so long and what a CPUit is. We're going to be taking you through a deep-dive on the company'sbrand new high performance Zen CPU microarchitecture, its features, specs and its performance.

Ryzen, AMD’s Most Important ProductIn More Than A Decade

Many Years In The making

The journey of the Zen microarchitecture, which sits at the core of every Ryzen chip, has been a long and challenging one.It’s the company’s first attempt to compete at the high-end, enthusiast, CPU market since the introduction of the Bulldozer microarchitecturefive years ago. Zen breaks new ground for AMD in many ways. It’s thecompany’s first ever CPU architecture to feature simultaneous multithreading.It’s alsothe very firstCPU for AMD to be built on a process technology that's very close toparity with Intel since the days of the original Athlonmore than a decade ago.

It means that forthe very first time since the early 2000s AMD’s CPUs areno longer atan inherent disadvantage due to Intel’s process lead. From an architectural point of view Zen is a brand new clean-slate design that’s been led from the get-go by accomplished CPU architect Jim Keller. The very same engineerthat played a pivotal role in designingthe original Athlon XP and Athlon64 processors, the most successful and competitive CPUproductsinthe history of the company.

Zen is AMD’s biggest long-term technology bet and one of the largest engineering efforts undertaken by the company. Design work on the microarchitecture began in 2012 and was completed four years later.The very first products based on the brand new CPU core design are Ryzen processors. Which are set to launch at the end of the month. However, we know that AMD is working on far more than just high performance desktop CPUs. The company has a 32 core Zen server CPU, a sixteen core Zen HPC APU and a quadcore Zen consumer APUcalled Raven Ridge. All of these products have been in the works since the very beginning.

The Zen Microarchitecture

Below we havea visual representation of an actual Zen core on silicon. The core is comprised of one floating point unit and one integer engine. This is a huge step away from the Bulldozer design, which featured two integer engines and one floating point unit per core. Each integer cluster in each Zen core has six pipes, four ALUs (Arithmetic Logic Units) and two AGUs which is short for Address Generation Units.

These AGUs can perform two 16-byte loads and one 16-byte store per cycle via a 32 KB 8-way set associative write-back L1 data cache. According to AMD the move from a write-through to a write-back cache has noticeably reduced stalls in several types of code paths. The load/store cache operations cache in Zen also reportedly exhibit lower latency compared to the4th generation Bulldozer core Excavator.

Bulldozer's relatively power hungry and slow cache hierarchies were one of the key factors in its poor single threaded performance and power efficiency. A lot of work has gone into designing a new cache sub-system for Zen to minimize the powerand area footprints as well as make it as fastas the silicon will allow.

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The L2 and L3 caches were grouped in a very clever way to minimize the access times by anygiven core at any given time. The write-through cache architecture has also been forgone in favor of a more power and area efficient write-back cache.

Another key area Zen differentiates itself from the Bulldozer family of cores is through its access to a relative abundance of L3 cache. Each Zen core has access to twice the capacity of L3 cache compared to AMD's last 8-core chip code named "Orochi". The infamous chip that we've come to know as the FX8150 and later as the FX 8350 and their derivatives.

The floating point unit is capable of performing two FMAC operations or a single 256-bit AVX operation per cycle. Exactly as we had detailed in our exclusive architectural deep-divelast year funnily enough.

AMD's First Microarchitecture To Feature Simulataneous Multithreading

The companyhas done away with the CMT - clustered multithreading - concept that was introduced with the Bulldozer family of cores in 2011 in favor of a more traditional SMT - simultaneous multithreading - design. This means that each Zen core will be able to execute two threads simultaneously. A primary very high throughput thread and asecondary thread with less oomph that can be used opportunistically.

In contrast, each Bulldozer module can execute two identical threads. This is achieved through two separate integer clusters with a single front-end. This approach saves area versus building two separate cores and delivers two high throughput threads. However, there are advantages that Zen's SMT implementation holds over the Bulldozer CMT implementation. For one it allows AMD to build a single larger integer cluster with significantly higher single threaded performance. Another advantage with this approach is that it leaves a lot of wiggle room for clever savings in area and power.

Incredible Drive For Power Efficiency

AMD's 8-core Ryzen chip has an army of sensors buzzing away to monitor voltages, temperatures, frequency and overall power at any given moment. These sensors are part of what AMD dubs its SenseMI family of technologies. We'll talk about these technologies in much more detail further down. It's these little engines that bring amazingly cool technologiessuch as the auto-overclocking XFR feature from the realm of science fiction to reality.

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