Supported CPUs are all AMD Zen2 based CPUs and some high-end Intel Xeon. There's a new option in config.json called cache_qos which controls it. If you set it to true, all CPU cores which are not mining will not have access to L3 cache which will reduce interference with mining. This feature requires MSR mod enabled and active.
Don't expect any significant hashrate increases and maybe even slight reduction on Xeons, this is why it's disabled by default. About 1% increase in some cases on Ryzen 7 3700X:
6 cores mining, 2 cores used for browsing/watching Youtube - 1% hashrate increase (or rather smaller hashrate hit from browsing).
Mobile Zen2 CPUs and upcoming desktop Zen2 APUs will have more cores than L3 cache for RandomX, so this feature will be very handy there because there will always be unused cores which can interfere with RandomX data in the L3 cache.