I was upgrading my 3600X to a 3900X and everything was going great when my PC suddenly shut down and went to a black screen. It refused to post even into the bios. It would hang on the boot sequence, code 90, with a white light determining VGA error. Installing my old processor resolved this issue.
At first, I suspected an MB failure, however, it boots and runs normally, upon reinstalling the 3600X. This is on an Asus Rog Crosshair Extreme VI, with updated bios 8002. The 3900X is listed on the Asus Board's site as compatible. It's possible that the 3900X CPU is malfunctioning! I will check it on another board tomorrow and see if it gives the same issue.
In the meantime, if anyone has had this issue it would be great to hear from others on their solution.
I suspect that you may need to update your bios. I have the Rog Crosshair Vl EX, X370 board, and I had similar issues when I tried to change my CPU from a 3600X to a 3900X. I believe the present Bios is 8503 on my board. Btw, it now accepts a 5800X3D which I've been considering upgrading to.
Nah! Lol! Didn't realize it until you pointed it out. My reply was supposed to be to another post with the same heading. Not sure how that happened?
The post in my post was what the other poster had posted. Go figure? Maybe I can track the original poster down or a mod can do it if I'm not able to myself.
As mentioned in the post above, try updating your BIOS. If this doesn't help, there's a huge chance of CPU being defective. This is strange anyway, since 3600 and 3900 are the same generation of Ryzen, therefore such issue shouldn't be a thing.