PC Graphics

[OX-Fenris]

I have just put together two nearly identical builds. Both builds are running AMD 5900X CPU's one is using the MSI X570 Tomahawk motherboard and the other has the MSI B550 Tomahawk. Both are running Corsair 850X power supplies. Both have the Saphire Nitro+ RX 6950 XT. The X570 build went together with no issues. Sadly the B550 build will not post if either of the 8pin power connectors are connected to the graphics card, it will post with only the 6pin connected but displays a motherboard VGA failure led.

[elstaci]

Sound like a power or PSU issue or defective Mobo PCIe slot.

Since the GPU Card works fine on th X570 Board with the same PSU but not on the B550 Board indicate a power issue when you connect both GPU power cables.

First I would try both GPU cards on both Motherboards to eliminate a defective GPU card. If both works fine on the X570 Mobo but doesn't boot on the B550 Mobo indicates either a defective PSU or Mobo.

It would be a royal pain to switch PSU between Mobo to see if the same thing occurs or not. But if you install the X570 PSU on the B550 Mobo and the same thing occurs would indicate a defective Motherboard (PCIe slot).

Try install the GPU card on the second PCIex16 slot (PCIe 3.0) to see if it boots up. The first PCIe Slot (PCIe 4.0/3.0) is powered by the CPU and normally the second PCIex16 slot is powered by the Chip set.

Expansion Slot

• 1x PCIe 4.0/ 3.0 x16 slot (PCI_E1) ¹
• 1x PCIe 3.0 x16 slot (PCI_E3), supports x4 speed ²
• 2x PCIe 3.0 x1 slots

1. The supported specification depends on installed processor.
2. When installing devices in M.2_2, PCI_E2 & PCI_E3 slots at the same time, PCI_E3 slot will be unavailable, and M2_2 slot only supports PCIe x2.