AMD Ryzen 9 3900X AM4 CPU Review

Memory, Overclocking & Power

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.

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

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

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

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.

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.

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

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

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

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

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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