Question Ryzen 9 5900x not working.

Cannon147

Prominent
Jan 23, 2023
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I'm upgrading from a Ryzen 7 2700x to a Ryzen 9 5900x, PC turns on but doesn't give any signal to monitors/mouse/keyboard/etc with the Ryzen 9.

I'm using the exact same setup with the new CPU as the old one, but I've tried the two motherboards and two types of ram listed below.
All the combinations of ram and motherboards work with the 2700x except with MSI x570 and the DDR4-3600 for some reason.

The latest bios was flashed after installing the 5900x in the b550. My first instinct is that the bios is causing the issue, but I'm not really sure how it could be and I don't know my way around the bios well enough to mess with it too much.

There is also no visible damage to the cpu, I've examined it closely and carefully and it at least appears to be in perfect condition to me.
Could the CPU be defective from the supplier (amazon)? I assume not though, and it's probably just something I've messed up on.

I am currently using the PC with the Ryzen 7 2700x and it is working normally.

Specs:
Motherboard: MSI B550 tomahawk (or MSI X570 gaming plus, which is what I had before)
RAM: 2x16GB Corsair Vengeance DDR4-3600 (or DDR4-3200)
GPU: NVIDIA GeForce RTX 2080 SUPER
PSU: EVGA 750 GQ
OS: Windows 10

I appreciate any help, thanks.
 
Last edited:

Barty1884

Retired Moderator
The latest bios was flashed after installing the 5900x in the b550.

Did you use BIOS flashback (or similar, I forget MSIs naming for it) with the 5900X installed?

Do you still have the 2700X? If so, I'd pop it in the board you want to use (B550?), see if it posts. If so, enter the BIOS and see what BIOS revision is installed. Should be on the main BIOS page. If it's a BIOS revision compatible with the 5900X, then re-socketing it may just 'work'. If it's not, update the BIOS from the BIOS, with the 2700X. Once it's complete, shut down, switch CPUs and see.
 

Cannon147

Prominent
Jan 23, 2023
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515
Did you use BIOS flashback (or similar, I forget MSIs naming for it) with the 5900X installed?

Do you still have the 2700X? If so, I'd pop it in the board you want to use (B550?), see if it posts. If so, enter the BIOS and see what BIOS revision is installed. Should be on the main BIOS page. If it's a BIOS revision compatible with the 5900X, then re-socketing it may just 'work'. If it's not, update the BIOS from the BIOS, with the 2700X. Once it's complete, shut down, switch CPUs and see.

Just made sure my bios was up to date with the 2700x in the b550 and then switched to the 5900x, same thing happened, the PC turned on but gave no signal to anything.
 

andrew3d

Prominent
Oct 25, 2021
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Could the CPU be defective from the supplier (amazon)? I assume not though, and it's probably just something I've messed up on.

I was just now thinking it was bad from Amazon. Are you still within the return and request it be replaced window?
 
Exactly which motherboard are you using? (it's just that I dont believe the B550 board will work with a 2nd gen cpu?) So if you tried updating the B550 BIOS using the 2700x, I dont think it will work? But the B550 does have BIOS Flash so you should be able to upgrade the BIOS that way.