CPUs are intentionally engineered for a target market. When engineering the M2, Apple had a certain market in mind, and design and performance trade-offs were made accordingly. As others have noted, power efficiency seems to be a big priority. The M2 Ultra has a TDP of 60W. The i9-13900K has a base consumption of 125W, and draws up to 253W under stress. So do the math. Intel achieves 32% better single-core performanc…
But of course, combining any number of M2’s won’t increase their single core scores. Intel’s desktop chips are there for people who want high clock speeds and are happy to pay in power for that (and the power cost is super linearly related to clock frequency). The Intel chips are just designed for different use-cases, it doesn’t make sense to assume either company could just linearly scale things to reproduce each other’s products.
The relevance of multi-core scores depends on how parallel the workload is. If we all had perfectly parallel workloads I guess Xeon Phi’s would have sold better.