Uncore is ReaL!!!
I guess its not as bad anymore eh?
With Coffee Lake, the CPU cache, ring, and uncore all change the same setting in the CPU. The ratio mainly changes the cache speed, and some vendors have this turned up to 4.4GHz by default. While you won't be able to match the CPU core multiplier most of the time, you should be able to stay 4-6 multipliers below the CPU core multiplier without requiring too much extra voltage. I always overclock the CPU up to it's maximum and then go back and find a cache multiplier that doesn't require more VCore to stay stable. And with Coffee Lake the VCore also provides power to the cache region and isn't a separate voltage rail like it was in the past.
As for OP's question,.. depends on your cooling solution, motherboard vendor. Some vendors allow you to choose the core setting mode, such as the ability to sync all cores or set the cores individually,.. I prefer using the sync all cores setting,.. on Asus, the board will auto-change to sync all cores if you set XMP to enable as it's enabling multi-core enhancement all the way.
Edited by Braegnok, 20 December 2018 - 03:07 PM.