AMD Ryzen 9 3900X AM4 CPU Review: Page 6 of 7

Posted by Damon Bailey on Sunday, July 7, 2019 - 9:01am

Memory, Overclocking & Power

AMD Ryzen 9 3900X

One of the biggest complaints with the previous generations of Ryzen processors was a lack of support for high-speed memory when every little bit higher than you could push the memory, the more overall performance you would see. AMD has used a new memory controller this generation to combat this and advertises fast memory is supported with ease. This comes with a small caveat though, anything over 3733 Mhz would shift gears and would drop the Infinity Fabric to Memory ration back to 2:1 instead of 1:1.

AMD Ryzen 9 3900X

We did all of our testings with 3200MHz memory, something that itself was a struggle to achieve on the first generation.

AMD Ryzen 9 3900X

During testing, we see the Ryzen 9 3900X routinely hit upwards of 4.6GHz thanks to XFR.

AMD Ryzen 9 3900X

We start out overclocking at 4.22 GHz all core speeds and get a decent jump over the stock score of 2968

AMD Ryzen 9 3900X

We can get 4.3GHz stable on all cores, but anything over about 4.35GHz we just can't quite get stable. We still see a decent score increase.

AMD Ryzen 9 3900X

We tried ramping the memory speed up, but even at 4266MHz, the fabric clock to memory clock ratio drops back to the point that we don’t see a gain.

AMD Ryzen 9 3900X

We tried ramping the fabric clock up to 1800MHz from 1600MHz and get a small bump in performance.

AMD Ryzen 9 3900X

To avoid the fabric to memory ratio change, we’ll drop back to 3733MHz and start cranking down timings. We get the above.

AMD Ryzen 9 3900X

Pulling the timings down to 3733MHz C14 we don’t really see much of a change.

AMD Ryzen 9 3900X

Even tightening up the sub timings doesn’t really gain us much.

AMD Ryzen 9 3900X

Power consumption is actually really great here. We see pretty close to the same power usage as last years flagship 2700X, but significantly less than many 6 and 8 core CPU’s as well.

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