AMD's Ryzen 5800X3D isn't set for release until April 20, and reviews weren't scheduled to go out until close to that date, but some publications who managed to get hold of the chip through uncertain means have begun publishing early reviews that show it to be a very capable CPU. In fact, it's even managed to eclipse the Intel 12900K in some gaming benchmarks, potentially making it the fastest gaming CPU in the world.
The 5800X3D is an intriguing CPU. It's a standard 5800X in almost every way, with the same eight cores and 16 threads, though with a lower 4.5GHz clock speed to offset voltage concerns over the new additions. Those additives come in the form of an extra 64MB of L3 cache that's bolted on top and works in parity with the existing cache. The result in modern games was dramatic, with some tests showing as much as a 40% increase in FPS at 1080p. Those results weren't common, though, with the uplift averaging out to around 10% across most games.
That's enough to give the 5800X3D the edge over the Intel 12900K, though, which costs as much as $150 more. It even makes it competitive with the 12900KS, though that higher-clocked chip will still sometimes steal the crown back.
The 5800X3D is expensive, especially considering you can get a 12-core 5900X for the same kind of money, which will be much better in productivity tasks like video editing. But if you're already on an AMD system and want to upgrade to cutting-edge performance for gaming right now, rather than wait for Zen 4 later this year (which will mean a full system upgrade) then the 5800X3D is a great buy.