AMD Ryzen 9 3900X CPU Review

Energy Efficiency and Power Consumption

Of course, one of the biggest architectural improvements to the 3rd generation Ryzen is the process node shrink or die shrink as it is more commonly known. Not only does this increase the transistor budget and allow for more cache and cores in the package, it also potentially reduces power consumption and heat. This is what AMD calls its: “7nm Energy Efficiency Leadership.”

Here are some points on this taken directly from AMD:

  • The higher natural performance of the “Zen 2” architecture dovetails beautifully with the superior performance, power, and density characteristics of the 7nm process. Some key metrics specifically enabled by the process change include:
  • 29% smaller CCX size vs. 12nm (~31mm² vs. ~44mm²), enabling new area for the “Zen 2” revisions
  • Up to 75% higher perf/W compared to 2ndGen AMD Ryzen™ Processors with the 12LP process
  • Up to 58% higher perf/W compared to 9th Gen Intel Core processors with the 14nm++process
  • 2X L3 cache size (32MB)vs. 2nd Gen AMD Ryzen™ Processors, not previously possible in the area with 12nm
  • Up to 2X more cores in the same package (AMD Ryzen™ 9 3950X vs. AMD Ryzen™ 7 2700X)
  • Up to +350MHz of core frequency at the same voltage vs. 12LP Altogether, these highly desirable characteristics position the 3rd Gen AMD Ryzen™ processor as the leader in desktop energy efficiency in 2019.
  • You can see this proven out for yourself in the below data, where AMD commands full-stack leadership over 9th Gen Intel Core in performance per watt.

AMD shows up to 58% greater performance per watt compared to Intel’s Core I9 9900K. AMD has similar claims across the product stack showing 30% better performance between the Core i7 9700K and the Ryzen 7 3800X. Meanwhile the Ryzen 7 3700X gets a whopping 56% performance per watt advantage compared to the i7 9700K. This one isn’t surprising at all given that the 3700X is the 65w TDP part.

More importantly, comparing the Ryzen 7 2700X and the Ryzen 7 3700X shows a massive 75% advantage in favor of the latter. Its important to note that the Ryzen 7 3700X has the same core and thread count, but also has higher clocks than the 2nd generation Ryzen 7 2700X. Naturally, these are claims we would like to test at some point. So far, preliminary monitoring I’ve done shows our test Ryzen 9 3900X using about the same or slightly less power than the Intel Core i9 9900K. This is a claim that’s somewhat hard to test as you can’t exactly get an “apples to apples” motherboard configuration. The test motherboard we are using for the Intel side is an ASUS ROG Maximus XI APEX. That is a board with 14 phases and no phase doublers. Its designed to provide massive amounts of power to the CPU for LN2 overclocking if necessary. In contrast, the MSI MEG X570 GODLIKE is no slouch for VRMs, but it also has a ton of integrated hardware that the APEX doesn’t.

Having said that, we did test this. Unfortunately, we didn’t have time to test each system. We felt it was prudent to test AMD’s claims vs. processors at the same price point primarily. That is how AMD represents its data after all. Therefore, we put Intel’s Core i9 9900K up against AMD’s Ryzen 9 3900X. Both processors have an MSRP of about $499.99 at the time of this writing. These are also each company’s highest end mainstream desktop offerings. Each system has a different motherboard and RAM. Their OS SSD’s are also slightly different. However, the systems share the same storage drive, graphics card, and power supply. The cooling hardware is identical from a power perspective. Lastly, each system was tested at their base / boost clocks as well as a manual “all core” overclock. The measurement was conducted with a Killawat meter and the power reading was taken at the wall. This is for the system only as the monitor was powered by a different outlet.

For load testing, we used Cinebench R20 and conducted a full run of the multithreaded benchmark. The power readings were taken in the middle of the test. This is the same application AMD used for its load testing in its reviewer’s guide.

As you can see, our Ryzen 9 3900X actually idles with a slightly higher power draw than our Intel system. However, under load things switch around. It’s important to note that the AMD system has a motherboard with far more integrated features, and its possible that some of that difference is easily due to the motherboards added complexity.

While overclocked, our Ryzen 9 3900X once again pulled a bit more power than the Intel test system. However, AMD’s claims are not about raw power draw but rather “performance per watt.” By that metric, AMD is more efficient as it’s offering has far greater core density and performance in multi-threaded workloads. I’m not seeing math that tracks with what AMD’s claims are, but as I said this was a test based on our limited selection of motherboards. At the time of this test, I had only one X570 motherboard on hand and it was the MSI MEG X570 GODLIKE which has features like a tiny LCD readout that shows a cartoon of a dragon fighting ninja’s or something.

Features like this create additional power draw. In contrast, the Intel system is using an ASUS ROG Maximus XI APEX, which is by comparison a stripped down no frills and no nonsense motherboard. The APEX motherboard has beefy VRM’s sure, but we aren’t pulling the kind of power they are capable of delivering under more extreme circumstances. It’s probable that using the right motherboards for comparison that AMD’s math would be a bit closer to its claims. I do agree that AMD offers more performance per watt, but your mileage may vary as to just how much more performance per watt you get in a specific combination. I long for the days when AMD and Intel used the same sockets and chipsets. It made comparisons like this much easier.

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