Likely a bios update you need to apply. At one point the B450s weren't going to support Zen 3. AMD reversed course later, but that likely means that a bios update had to come along in order to add the support.
Lots of motherboards, even new ones, still ship with old-ass bios.
Also, remember that memory-training is a thing now -- don't assume that 10 seconds of a black screen means it won't post. Easily wait a minute or more - board could just be in memory-training to get the best speeds.
Some boards even have a light indicating this is occurring!
Excellent upgrade!! 😃 That's wonderful you got the new CPU, you will notice a differencein spped in everything immediately!
Take out the 5700x3D, put 2600 back in and repaste heatsink. Turn on computer flash BIOS to the last version available for B450 Carbon AC. Read BIOS revisions notes to see if any say do not skip ahead until flashing this version of BIOS because if say version 103 says do not jump to lastest before updating to this version but you only flash version 110, there will be a problem with motherboard because info in BIOS is missing so board can't boot normally.
But if you flash version 103, wait for it to finish, reboot, flash version 110, wait for it to finish, reboot, wait for desktop, then you should be 100% good for board to boot 5700x3D. Those version numbers are made up examples, don't go looking for those BIOS version numbers on the MSI page
I guess i will try this, maybe I missed some update
If you put 2600 back in, update BIOS, please post an update on how it goes.
In the description f the BIOS version, it will say something like "Support new Ryzen 5000 CPU", that's what you want before puting 5700 back in motherboard, but I suggest going to last version of BIOS that you can flash so you can be done permanently from flashing anything since there's no more support for AM4 platform, maybe only the odd fix
Video of how to update MSI BIOS here
This is the plan. The thing is I can't fins ryzen 5000 support on the mobo page, only 3000
Uh oh, I looked at MSI page for your board, and there's no support for 5000. The parts for that motherboard must be too cheap to comply with AMD's hardware requirements for motherboard manufacturers. You can't use your 5700x3D without buying a better or newer motherboard. If you buy a B550 you could flash BIOS and use 5700. Either sell your 5700x3D or buy a better motherboard since there's no support for 5000
Ans yet, on the compatibility list, they say it is ok with latest bios, and some people said they were running it on a b350m pro. I will probably try the flash route tomorrow. This is weird. Also, this mobo was praised for the cpu power management as being overly overengineered...
Sure, put your 2600 back in and then flash it to the last one, but do a test boot with 2600 of the lasted bios to verify that the board is still good and boots to desktop on the latest version, and then put in your 5700x3D. If it boots, you got it, if it doesn't boot to desktop with the latest bios then you know it wlll never work
I'd say look up the processor compatibility list for the motherboard. It could be that the motherboard doesn't directly support that processor.
I just checked for you, the 5700X3D is supported by your mobo with the latest BIOS version. Double check it is the latest BIOS. Reseat the processor, don't overtighten the heatsink, this is a common cause of issues. Remove all RAM, then reinsert 1 stick only. Unplug all USB devices when booting.
I had this issue, you need to update the bios. However, I couldn't even get it to show up on the monitor, I had to correctly format a USB drive with the update and use the red "flash bios button"