AMD Ryzen 9 3900X Review 173

AMD Ryzen 9 3900X Review

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AMD today released its 3rd generation Ryzen desktop processor family based on its "Zen 2" microarchitecture. The company surprised everyone with its "Zen" desktop family because expectations from AMD on the processor front had faded due to a decade of Intel's unchallenged market dominance and its eventual stagnation in per-core performance growth over the past few years. Something as simple as a 4% IPC uplift from AMD for its 2nd generation "Zen+" processors was met with cheers as Intel began waking up to the reality of a resurgent AMD. Wafer supply woes causing price hikes shielded AMD from Intel's 8th generation Core. Intel fought back with the 9th generation Core processors, but pricing and supply issues in the desktop retail channel pushed sales to AMD. Fast forward to mid-2019 and AMD is in the thick of things.

Today, AMD is not only launching its 3rd generation Ryzen processors, but also its Radeon RX 5700 "Navi" graphics cards. What's common between the two is the 7 nanometer silicon fabrication process they're built on, which is significantly more advanced than the 14 nm process Intel has been stuck with. With Intel's upcoming 10 nm "Ice Lake" processors arriving no sooner than 2020 for the desktop platform, AMD is eyeing a free rein on the market for a good three quarters by releasing "Zen 2" with the idea of toppling Intel's 9th generation Core processors at every price point.

At the heart of AMD's effort is the "Zen 2" microarchitecture, which sets out to match or exceed the IPC of Intel's latest "Coffee Lake" microarchitecture. This would be the first time in over 15 years that AMD beats Intel at IPC. While Intel led AMD at IPC, AMD led Intel at CPU core count. Intel responded to previous generations of Ryzen processors by increasing core counts of its mainstream desktop processors for the first time in a decade. With the 9th generation Core, Intel achieved core-count parity. AMD's response is not only matching the 9th generation Core at IPC, but also restoring AMD's competitiveness by increasing core counts, at least in the high end. Intel gave its coveted Core i9 brand extension to its 8-core LGA1151 processor. AMD created the new Ryzen 9 series to match the Core i9 LGA1151 at price and IPC, while beating it at core counts. We hence have the Ryzen 9 3900X and the upcoming 3950X.

The Ryzen 9 3900X is a 12-core/24-thread processor, a 50% increase in core counts right off the bat against the Core i9-9900K. The Ryzen 9 3950X, which will join the product stack this fall, is a 16-core/32-thread monstrosity priced at $750, while retaining its mainstream-desktop credentials. Such high core counts are possibly not only due to the switch to 7 nm, but also because AMD has taken the multi-chip module (MCM) approach to building these processors, which are both similar and dissimilar to the Ryzen Threadripper. They're similar in that the CPU cores are spread across two separate dies. They're dissimilar in that there's a second kind of die, the I/O controller.

With its first EPYC and Ryzen Threadripper processors, particularly the high core-count WX models, AMD ran into several structural problems with memory bandwidth sharing between the CPU cores. The company fixed these with its 2nd generation EPYC processors in which all dies with CPU cores talk to a centralized I/O controller die that has a monolithic memory controller, thereby making it possible for a CPU core to have the full bus width of the memory interface. With its 3rd generation Ryzen processors, AMD takes a similar approach. Two 8-core CPU complex dies talk to an I/O controller die over Infinity Fabric, which has the processor's dual-channel memory interface and PCI-Express root complex.

The reasons for not building a monolithic 16-core die on 7 nm are economic. AMD is contracting TSMC to build its 7 nm wares, and it would want to minimize its silicon design to the smallest indivisible unit, an 8-core "Zen 2" chiplet. The company can build socket AM4 Ryzen processors with one or two of these chiplets to achieve up to 16 cores or drop up to eight of these on an SP3r2/TR4 package to achieve up to 64 cores. To minimize redundant components like with MCMs that use "Zeppelin" dies, AMD disintegrated the memory controller, PCIe root complex, and integrated southbridge on to the I/O controller die. This die has components that aren't as power critical as CPU cores, so AMD could build it on the existing 12LPP (12 nm) process at GlobalFoundries. The Ryzen 9 3900X is an MCM with two 7 nm CPU core chiplets, and the I/O controller die. Models that have 8 CPU cores or less, such as the Ryzen 7 3700X or the Ryzen 5 3600X, only have one 7 nm chiplet besides the I/O controller die. This way, AMD makes the most out of its limited allocation at TSMC, which is building 7 nm chips for a dozen other companies.

In this review, we have with us the Ryzen 7 3700X, an 8-core/16-thread processor launched at the same $329 price as the 2700X and over $50 cheaper than the Core i7-9700K. Besides a higher core count and similar IPC, these processors offer the latest PCI-Express gen 4.0 bus, which doubles bandwidth for graphics cards and SSDs that support it.

Our exhaustive coverage of AMD's 7/7 Launch Day includes the following content:
AMD Ryzen 9 3900X 12-core processor | AMD Ryzen 7 3700X 8-core processor | AMD Radeon RX 5700 XT graphics card | AMD Radeon RX 5700 graphics card | AMD Zen 2 Memory Performance Scaling | Ryzen 3900X and 3700 on X470 vs X570 platforms | Radeon RX 5700 XT Navi PCI-Express 4.0 Performance Scaling | ASRock X570 Taichi motherboard | ASUS Prime X570-Pro motherboard

Ryzen 9 3900X Market Segment Analysis
 PriceCores /
Core i7-9600K$2306 / 63.7 GHz4.6 GHz9 MB95 WCoffee Lake14 nmLGA 1151
Ryzen 5 2600X$1706 / 123.6 GHz4.2 GHz16 MB95 WZen12 nmAM4
Ryzen 7 1700X$1708 / 163.4 GHz3.8 GHz16 MB95 WZen14 nmAM4
Ryzen 7 2700$2358 / 163.2 GHz4.1 GHz16 MB65 WZen12 nmAM4
Core i7-8700K$3656 / 123.7 GHz4.7 GHz12 MB95 WCoffee Lake14 nmLGA 1151
Core i7-9700K$4108 / 83.6 GHz4.9 GHz12 MB95 WCoffee Lake14 nmLGA 1151
Ryzen 7 2700X$2958 / 163.7 GHz4.3 GHz16 MB105 WZen12 nmAM4
Ryzen 7 1800X$2508 / 163.6 GHz4.0 GHz16 MB95 WZen14 nmAM4
Ryzen 7 3700X$3308 / 163.6 GHz4.4 GHz32 MB65 WZen 27 nmAM4
Core i9-9900K$4808 / 163.6 GHz5.0 GHz16 MB95 WCoffee Lake14 nmLGA 1151
Ryzen 9 3900X$50012 / 243.8 GHz4.6 GHz64 MB105 WZen 27 nmAM4
Threadripper 2920X$63512 / 243.5 GHz4.3 GHz32 MB180 WZen12 nmSP3r2
Threadripper 2950X$83016 / 323.5 GHz4.4 GHz32 MB180 WZen12 nmSP3r2
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