Build Advice CPU swap then no boot

Mar 13, 2021
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Like many, last fall I decided to build a new PC with all of the new components that were released. I got lucky and got a 3080 in Nov. But was not able to get a 5900x. So in December I just reused my current CPU (2700x). Everything worked well for the last 4 months. This also allowed me to upgrade the motherboard BIOS to 2802 to make it compatible with the new CPUs.

System specs:
MB: Asus Tuf Gaming X570 Plus with WiFi
CPU: AMD 5900x
Memory: GSkill Ripjaws V F4-3600C16D-32GVKC
GPU: EVGA FTW3 ultra 3080
PS: be quiet Straight Power 11 850w
SSD: M2 Samsung 860 EVO 1 TB

Last week I finally ordered a 5900x and got it last night. I carefully swapped the CPUs and redid the thermal paste. This was the only change I made. And now it will not POST.

The Q-leds show a solid white (VGA) and green (BIOS). No speaker in my case so not hearing any beep codes. Things I have tried:
  1. Tried different GPU output ports including switching to an HDMI cable.
  2. Tried the motherboard displayport and HDMI ports.
  3. Removed GPU.
  4. Switched back to old CPU and system posted. Confirmed BIOS version (2802) was compatible with 5900x on Asus website and it is.
  5. Switched to new CPU and no post.
Did I miss anything? I really don't want to have gotten a dead CPU.

djak
 
Mar 13, 2021
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You need to remove the CMOS battery for 10-15 minutes
Thanks for the clarification Fiorezy.

I removed the old CPU, removed the CMOS battery for 20 minutes (just to be sure), shorted the 'clear CMOS' jumper per the MB manual, put the battery back in, and put in the new CPU. When I reconnected it and turned it on it still did not POST. I swapped back to the old CPU and it did. Also asked me to set the time in the BIOS so I could tell it had cleared the BIOS this time for sure.

I have started a warranty replacement with AMD.

djak
 
Reactions: Master Djoza
Thanks for the clarification Fiorezy.

I removed the old CPU, removed the CMOS battery for 20 minutes (just to be sure), shorted the 'clear CMOS' jumper per the MB manual, put the battery back in, and put in the new CPU. When I reconnected it and turned it on it still did not POST. I swapped back to the old CPU and it did. Also asked me to set the time in the BIOS so I could tell it had cleared the BIOS this time for sure.

I have started a warranty replacement with AMD.

djak
Good luck!
 
Mar 13, 2021
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Update in case someone else has this issue.

AMD did send a replacement CPU and the problem still happened. So I installed an old GPU (since the board was signaling a VGA issue) and the computer did POST to the BIOS. So I light bulb went off that I am using a vertical GPU extension. And all extensions are only PCIE3. And the old CPU only supported PCIE3 but the 5900 supports PCIE4. So I directly installed the 3080 GPU and the computer now works. I decided not to mess around and see if I can get the vertical extension working and left GPU horizontal.

Thanks to all for their suggestions.
 

Karadjgne

Titan
Ambassador
In bios change the auto recognition of the gpu. The 5900x supports Gen4, defaults to that, as does the gpu, but having the Gen3 riser throws a wrench in the works as the board is trying to verify the bandwidth and failing, and you get the VGA error at boot.

So if you want to use the riser, just set the mobo up as Gen3 until you can get a Gen4 riser.
 
Reactions: djak

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