Initially rumored to hit 5.5 GHz on a single core, the i9-12900K might not be able to get turbo boosts higher than 5.3 GHz, at least according to the latest leaked qualification sample specs. Still, this does not appear to hinder the overall performance of the upcoming high-end Alder Lake models, as the multi-core scores in Cinebench R20 are rumored to be at least 800 points higher than the Ryzen 9 5950X.
https://www.notebookcheck.net/Intel-Alder-Lake-i9-12900K-qualification-sample-hitting-5-3-GHz-rumored-to-be-800-points-faster-than-the-AMD-Ryzen-5950X-in-Cinebench-R20-multi-core-tests.550917.0.html