You dont have to join any pads on Maximus 9 Extreme, just use CH341A programmer and connect it through JSPI connector (above JSPI you have 3 pins to choose which chip you want to flash, if you connect to each other left and middle pin you can flash 1st bios chip and if you connect middle and right one you can flash second chip). Try this bios: https://disk.yandex.ru/d/O6a5jdcdXaQKGg (supports every cpu, even 9900k with HT). Of course after flashing just unconnect every cable (especially the bios switch one)