PCIe connectors 3 and 4 only have 1 x 8 PCIe lanes. This creates a problem for cards that require 2 x 8 lanes.
Not all cards are supported in connectors 3 and 4.
- Verify the cards in I/O connector 3 and 4 are not cards supported only in I/O expansion connectors 1 and 2. The following link to the Service Guide describes cards supported only in I/O expansion connector 1 and 2.
- If the card is in the correctly supported connector, replace the card.