It's a rumor of the highest category this one, but a Chinese forum user claims to have a sample that reaches a boost clock speed of 5.3 GHz. At the end of this year, Intel will introduce the CPUs of Alder Lake; samples info will get leaked sometimes.
In any event, Core i9 12900K in question is an overclockable CPU with 8 Golden Cove cores and 8 Gracemont cores (BIG.little). In Cinebench R20's multi-threaded test he'd score about 11,300 points, which is 10% fasterer than a Ryzen 9 5950X.
The boost clock of 5.3 GHz is lower than expected, previously there were rumors of a boost clock of 5.5 GHz. The qualification sample designation means that it should perform more or less the same as the actual production model, while further improvements are possible for an engineering sample.
Twitter-based YuuKi AnS, says it does not yet have the full potential of Alder Lake, Windows 11 would be needed. This may have to do with the task scheduler since Windows 11 should better be able to handle CPU cores of various sizes. In addition, the frequency of the clock may still improve.