X470 Taichi not posting 7b or 76 code

https://www.tomshardware.com/reviews/corsair-cx750m-psu,4799.html

tomshardware rate it lousy :( :( :(

Unfortunately the 3800x isn't booting on my ga b450m too, seems more likely the cpu is dead, I'm just not sure if the motherboard may be killing the 3000 series since is the 3rd in 5mo and working just fine with the rest of them...

Yeah didn't work, did the update with the 1700, boot just fine everything was working, swap to the 3800x code goes 33-7a-7b(76)
:/

I got my second 3800X the first i had to rma due the same error, the store said the was an actually fault cpu send me a new one and the new one still giving me the same error, both 3800X, i though they where from the same batch but doesnt seems likely, since one was made in 2019 week 42 and this new one is 2020 week 6, i can boot with my fiance 1700 just fine all the memories are recognized go into windows or linux (dualboot) and game, i was using an 3700X for about 6 months which died (not instatly but took a couple of days crashing games but booting into windows fine and finishing cinebench tests just fine), for my mind sake i just want to make sure if the issue is the cpu again or the motherboard, like i said i can boot with the 1700, im using the 3.77 bios version since was the best the i´ve used (tried the 3.90 too with the first 3800X no successs).

I also tried to start with only one stick of ram and using different slots, same error, tried to start without gpu, same error.