Upgrade Ryzen 5 3400G to Ryzen 9 3900 on HP Elite Desk 705 G5 SFF

[New_Ryzen]

Hello everybody

I want to upgrade my HP ELITEDESK 705 G5 SFF with Ryzen 5 3400G to Ryzen 9 3900 (not 3900 pro but normaly is the same). After upgrade the PC running normaly but i have black screen. My graphic card work perfectly with the old cpu (Ryzen 5 3400G) I have upgrading my pc with the last firmware but no change. 

Someone have a good issue for my problem please?

Thanks a lot.

[DGroves]

check that you have the latest bios installed, HP lists the 3900pro as supported so your non pro 3900 is also supported

however note that the 3900 does not support onboard video, like the 3400G (G= onboard cpu video) as such a addin video card will be required and make sure the monitor cable is connected to the add in card and not the case's video connector

if a bios update does not resolve the issue and your current 3400g cpu works then the 3900 cpu is defective

https://support.hp.com/us-en/document/c06461848

[New_Ryzen]

Hello evervybody,

following the response given by Dgroves, I returned the processor to the seller and he tried it on a Gigabyte A520M K2 motherboard without updating the bios (see attached photo) and it works perfectly. Why does the processor not work on my motherboard knowing that it accepts Ryzen 9 3900 processors. I did everything correctly, updated the bios, Nvidia GEForce GT730 2 GB sff format graphics card. Have I forgotten something? Thanks a lot for your help.