Bottom line: Like AMD's first and second generation of Ryzen silicon, dialing in serious overclocks with Ryzen 3000 processors just doesn't seem to be possible, short of winning the silicon lottery.
AMD's Senior Technical Marketing Manager, Robert Hallock, has confirmed what most reviews have already uncovered: Ryzen 3000 doesn't offer a lot of overclocking potential. And according to Hallock, that shouldn't be a surprise, given AMD's investment in its Precision Boost 2 formula.
Hallock took to Reddit in response to questions regarding boost clock behavior and overclocking headroom. Hallock explains that AMD doesn't like to leave any performance on the table, and that its algorithms (that is, Precision Boost 2) are meant to squeeze every megahertz of performance from Ryzen 3000 silicon.
I'm not sure what you're asking. Our boost formula is opportunistic based on VRM current, socket power, temperatures. Therefore: light workloads will have a higher boost, and heavier workloads will have a lower boost. This is the basic behavior of Precision Boost 2 we described in November 2017. This is the same boost formula used for all Ryzen 2000 Series CPUs as well: 4.3GHz peak for light threading, to around 4GHz for all-cores. No change year-over-year in how the boost behaves.
If you're asking whether or not all cores will hit the max boost clock: no. It will not do that, nor have we ever promised or implied that. We've been very clear for 1.5 years that the Precision Boost 2 behavior is a "curve" that tries to get the loaded cores to the highest possible frequency with respect to the aforementioned limits. Even with all cores loaded, the CPU can maintain frequencies that are hundreds of MHz higher than base.
The other goal of our engineering effort is to absolutely maximize the performance of the product out of the box. //EDIT: By designing algorithms that extract the maximum silicon performance automatically (e.g. Precision Boost 2) without asking the user to tinker or risk their warranty. So, no, you're not going to see a whole lot of manual OC headroom. That's just performance an average person--who doesn't know how to OC--can't access. Why would we do that? It is not our intent to leave anything on the table.
It's more beneficial to enable PBO, overclock the fabric, overclock the memory. But that's true of Ryzen 2000 Series, too.
Indeed, TechSpot's own Ryzen 9 3900X, Ryzen 7 3700X and Ryzen 5 3600 reviews support Hallock's statement. We managed to achieve a 4.3 GHz all-core overclock with both the Ryzen 9 3900X and Ryzen 7 3700X -- one of the better manual overclocks out there. With our Ryzen 5 3600, we couldn't get past 4.2 GHz.
The news may be disheartening, depending on your perspective. For those wanting the best out of the box performance, AMD seems to have optimized the curve of Precision Boost 2 to extract an impressive amount of performance automatically. However, for enthusiasts who like to tinker with manual overclocking, there doesn't appear to be much room for playing with core clocks.
The 7nm process node is still in its infancy though. Once 7nm has had some time to mature, it may yield better silicon with more overclocking potential. In the meantime, it seems that enabling PBO and overclocking the memory and Infinity Fabric interconnect could net more positive results, as Hallock notes in his statement.