Ryzen 5900X vs. 3900X | Digital Tendencies

The new processors of the Ryzen 5000 series from AMD promise a significant performance improvement over the last generation. However, due to the specs, not much seems to have changed. This couldn't be truer than the Ryzen 9 5900X and 3900X, which both have 12 cores and 24 threads, the same 105W TDP, and only slightly different clock speeds.

The TSMC 7nm FinFET process stands behind both processors, although some clever redesigns from AMD give the 5900X an edge in some situations. But is the improvement enough? In this guide, we're comparing the Ryzen 5900X to the 3900X so you know which processor to use for your next build.

Prices and availability

AMD's Ryzen 9 3900X was released on July 7, 2019 with an MSRP of $ 499. At the end of 2020 there are still enough stocks of these processors at or below the asking price. We saw processors drop to $ 399 and only cost $ 300 in the second-hand market. The AMD website lists the current price as $ 464. While there is currently ample inventory, we expect AMD to phase out its 3000-series processors – including the 3900X – in 2021.

The Ryzen 9 5900X was announced during AMD's ZenD unveiling in October 2020 and released shortly after on November 5th. It's $ 50 more expensive and has an MSRP of $ 549 (the slightly less powerful Ryzen 7 5800X is $ 50 more than the last generation of competing chips). The stock is likely to be a problem a few weeks after it launches. However, we don't expect the stock issues to persist like the RTX 3080.

Specification for specification: a generation leap?

In a direct comparison of the technical data, the Ryzen 9 5900X does not look quite like the generation leap that AMD had promised. The newer AMD chip still has 12 cores and 24 threads, and while it has a higher boost clock, it's only marginally higher. Otherwise, the specifications are the same except for the size of the L2 and L3 cache and the total power consumption.

Ryzen 9 5900X Ryzen 9 3900X
Cores 12 12
subjects 24 24
Base clock 3.7 3.8 GHz
Boost clock 4.8 4.6 GHz
L2 cache 6 MB 6 MB
L3 cache 64 MB 64 MB
Unlocked Yes Yes
TDP 105W 105W

The numbers don't tell the full story, however. The Zen 3 architecture in the Ryzen 9 5900X has some major differences from Zen 2, the most important of which is direct access to the L3 cache. Instead of splitting the cache pool like Zen 2 chips, Zen 3 chips are drawn from a shared pool. In games or applications that use a dominant thread, this means that the thread has access to the entire pool of the L3 cache without having to walk across the cube. Instructions per clock (IPC) have also increased by up to 19% compared to third generation Ryzen.

Benchmarks for the new AMD chip are still rare. According to AMD's internal benchmarks, the 5900X clearly beats the 3900XT – the same chip as the 3900X with slightly faster clock rates – in Shadow of the Tomb Raider. The 3900XT averaged 141 frames per second while the 5900X pulled 181 fps at 1080p with high settings. AMD also showed frame improvements in League of Legends, Battlefield V, and Ashes of the Singularity – up to 50%.

Early GeekBench results support AMD's claims. In a benchmark, the 5900X achieved a single-core score of 1,681 and a multicore score of 14,613, and the benchmark shows that the 5900X goes beyond its boost clock to 4.94 GHz. In comparison, the 3900X achieved a single-core score of 1,299 and a multicore score of 12,381 in this test and only increased to 4.38 GHz.

Single-core performance has been a successful strategy for Intel for many years. However, that could change with the 5900X. Early benchmarks show the 5900X outperforms the 10900K in single-core performance (read our comparison between the 3900X and i9-9900K to see how Intel and AMD stacked up in the last generation).

While the 5900X specs don't look impressive compared to last generation offerings, early benchmarks look promising and the underlying tooling design supports the results we're seeing. While the 5900X is technically only $ 50 more than the 3900X, you'll likely be spending about $ 150 more if you opt for the newer AMD chip. We'll have to wait for more validated benchmarks to get the full story, but based on results so far, the 5900X justifies this higher price tag.

Should you upgrade?

AMD Ryzen 9 3900xRyzen 3000 CPUs Dan Baker / Digital Trends

The 3900X is still an excellent processor, and with its recent and frequent price drops, it is a great deal too. However, initial results speak in favor of the newer chip from AMD. The retired architecture of the 5900X allows the cores full access to the L3 cache pool, resulting in better per-core performance. Because of the update, we can see some significant IPC improvements that translate into higher frame rates in games and faster performance in productivity apps.

If you compare the two directly, most people don't sacrifice much with the 3900X (and they save around $ 150). However, there are a few other things to consider outside of price and performance. The 3900X is compatible with AMD's older 300-series chipset with a BIOS update, while the 5900X is only supported by the 500-series and 400-series chipsets (with a BIOS update). If you've left out the last few generations, you may need to upgrade your motherboard to a 5900X even though all three generations of chipset share the same AM4 socket.

That's a point against the 5900X, but there is also a point for it. The upcoming RX 6000 GPUs from AMD are equipped with Smart Access memory so that users with a 5000 series processor and a 500 series motherboard can give the processor direct access to the ultra-fast memory of the GPU. We don't have any third-party benchmarks for this feature yet, although AMD's internal benchmarks look promising. In Battlefield V with 1440p, AMD claims the RX 6800, 6800 XT, and 6900 XT all beat Nvidia's $ 1,500 RTX 3090 when all four are paired with a 5900X with Smart Access Memory enabled.

While these results are likely more than exaggerated, they demonstrate one of the benefits of introducing AMD's new platform. If you're building a PC from scratch or are ready to do a major upgrade, the 5900X is a better option. It has features like Smart Access Memory and is only slightly more expensive in all respects. However, if you just want to upgrade your processor, you may also need to consider the cost of a motherboard. In this case, it's best to stick with the 3900X.

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