[dragontamer]

https://www.mersenneforum.org/showthread.php?p=614191

> Since 512-bit instructions are reusing the same 256-bit hardware, 512-bit does not come with additional thermal issues. There is no artificial throttling like on Intel chips.

At least for Zen4, there's no worries about throttling or anything really. Its the same AVX hardware, "double pumped" (two 256-bit micro-instructions output per single 512-bit instruction). But you still save significantly on the decoder (ie: the "other" hyperthread can use the decoder in the core to keep executing its scalar code at full speed, since your hyperthread is barely executing any instructions)