Bios update

Hi. I have an Asus b550-f. I had already installed cpu. I entered bios it said new cou found. Then connected all my hard drives (sata). Set windows drive in bios boot menu. Repairing drive..... 1 hr later it restarted now I can't get into bios, tried flash back, didnt work, cmos battery taken out etc etc..seems to be a lot of people with same problem. So here's my question,, if I disconnect the cpu power cable, should in theory I should be able to get into bios then update it? Ps if I connect hdmi into I/O panel it fails post test, but if put into gpu it passes.