Question PC not POSTing, boot cycles only when SATA is plugged in ?

freshtodeath

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Sep 27, 2010
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I'm hoping to get some insight into what might be happening with my PC that I built. I've spent hours researching and troubleshooting to no avail. This is what I've done:
  • AMD Ryzen 5600x
  • RAM Corsair Vengeance PRO 16GB
  • MB: MSI B550 A Pro
  • Video: Asus TUF 3080
  • PSU XPG 750W
  • 2x 2.5" SSDs connected via SATA cables

  • I have a donor PC that I'm currently using. I have tested all parts on it except the CPU because the socket isn't supported.
  • PC was operational for over a month without issues.
  • Randomly during idle it shut off and does not POST (cycles reboot after a brief black screen with _ in top left) when any of the SATA ports are plugged in.
  • EZ debug shows VGA. Tested my card in another PC and it works fine. Used a working video card from donor PC in mine and it's doing the same thing.
  • I deducted that when SATA ports are unplugged it boots into BIOS and all hardware is recognized.
  • Tested my SSD in another PC and it boots into Windows (I'm booted into Windows on that SSD as I'm making this post)
  • Tested someones SSD in my PC and it does not POST when SATA is plugged into the MB
  • SSD can be plugged into PSU but not into SAtA in order to POST into BIOS
  • Flashed most recent non-beta BIOS
  • Cleared CMOS
  • Tested 3 GPUs
  • Tested 3 RAM sticks in single and dual configs
  • Lastly I RMA'd the mobo. I received the replacement board yesterday (same one, but serial# doesn't match what I had so I assume it's new or refurbished) and when I put everything back together it does the exact same thing it was doing before RMA - just cycle booting without POST with SSD plugged in.
I'm out of ideas regarding what might be causing it. I'm about to just buy another mobo. Does anyone have any ideas on what might be causing this issue?