[baybal2]

1. They are physically huge, and that means more leakage, when there could be none.

2. Inefficient front-end taking toll on everything behind it contributes to the rest of the chip doing nothing except dissipating power.

3. While cores on modern SoCs take much less space than everything else usually, front-ends still eat into the die area.

4. Front-end dictates how the rest of the core behind it is designed. I believe that X86 technical debt absolutely must exert its toll on that, and overall transistor count in the back-end.

[zsmi]

It's big, but not overwhelmingly so. To eye is looks like it's about 10% of the area so it jives with the quote provided by minipci1321 which claims ~10% of power.

Here is an annotated die shot of Zen2 that shows it. https://forums.anandtech.com/threads/annotated-hi-res-core-d...