A benchmark preview of the Intel Core i9-12900K has been accidentally posted online, and it shows the 12th Gen Alder Lake hybrid chip offering a seesaw-like performance against the Rocket Lake i9-11900K. While the engineering sample does show promise even without the AVX-512 instruction set, it could not shine against the AMD Ryzen 9 5900X Zen 3 part.
https://www.notebookcheck.net/Seesawing-Intel-Core-i9-12900K-sample-with-disabled-AVX-512-teeters-against-the-i9-11900K-in-preview-benchmarks-and-fails-to-overwhelm-the-AMD-Ryzen-9-5900X.566088.0.html