TechPowerUp posted a review on the Intel i7-8700K Coffee Lake Memory Benchmark Analysis
A quote from the article:
We take a close look at memory speeds, latencies and command rate on Intel's latest Core i7-8700K with Z370. Scenarios tested include fail-safe 2133 MHz, the platform default of 2666 MHz and overclocked memory speeds from 3000 MHz to 4000 MHz - at various timings.Intel i7-8700K Coffee Lake Memory Benchmark Analysis @ TechPowerUp