Undervolting now works for me on my Strix B660-I and 13600K using the latest BIOS (2212). They added the option to change the microcode to an other version to get rid of all the nonsense Intel did to their CPUs.
First you have to change the microcode from "Current Microcode" to "0x104 Microcode"
Doing this enables you to set an offset to "Global Core SVID Voltage" and "Cache SVID Voltage".
Leave "Actual VRM Core Voltage" on Auto!
Cinebench R23
Single: 2006
Multi: 23700
CPU-Z Bench
Single: 830
Multi: 9800
So pretty much the expected scores for a stock 13600K.
I set the offest to -150 mV because the latest Bios increased the stock voltage even further to around 1.4 Volts. Looks stable to me so far.
This thread over on Techpowerup pushed me in the right direction:
https://www.techpowerup.com/forums/t...erated.304802/
Should also work with B760-I. You don't have to use Throttlestop, but that's also an option.