Hi,
I’m totaly new to UEFI modifications - I have an ASUS-KNPA-U16 and a partial working EPYC ROME QS 32C (ZS1711E3VIVG5 ) where 5 (#4, #8, #10, #16 and #19 (start counting at #0)) cores throw errors (so they are defect).
I am able to boot Linux with maxcpu=1 kernel argument, and then reenable the working cores later on. But I’d like to mod my UEFI, so the defective cores are disabled on boot by UEFI (and not by the OS).
Is there anyone with knowledge, how to disable specific cores? (In AMDs CBS menu there exists the function to “downcore” the cpu, but it’s not possible to decide which specific cores to disable).
I know that the main work has to be done by myself, but maybe one of the modding cracks here would like to do some chat/videocall with me 
I have found a thread where something similar is done with an old Phenom II X6:
https://forums.anandtech.com/threads/dis…ttings.2447713/
so what this setpci command does should be able to do early in uefi? And how to get the correct address and bytes to do so?