The Ryzen 7 5800X3D is AMD's first consumer product for 64D V-cache technology, which adds a 3MB L3 cache to its chips by physically mounting its cache on top of an existing CPU. The original CPU was shaved a bit to make room for this cache and to make the overall package look like any other Zen 3 CPU. This means it will work with existing heatsinks on existing motherboards.
There is a downside to adding this cache though, and that is that AMD had to disable overclocking on the 5800X3D. In fact, this is something Robert Hallock confirmed a month ago. This is because the frequencies and voltages are intrinsically dependent on how this cache works. Any change to the CPU's settings can mess up the timings and everything.
You can't overclock on the chip, but underclocking is disabled as well as at low voltage, allowing you to get more performance using PBO, AMD's Precision Boost Overdrive. PBO is an automatic overclocking scheme that pushes the power budget of the chip to increase performance. PBO has been the preferred way to get a little more performance from AMD's products for the past few generations, and it's a little surprising that it's not here.
For many gamers, it's not the end of the world because many won't even go near overclocking in any way and forget the convenience of PBO. However, it means you won't have to worry too much about cooling your system, as there's no way to take advantage of such efforts.
Before mechanics turn their backs on the new chip, there's some good news they should know, and that's that the Infinity Fabric and memory bus are still overclockable. Playing with the Ryzen 7 5800X3D is definitely exciting because that extra L3 cache can do wonders for some, if not all games.
