Intel Desktop Board 21 B6 E1 E2 Specification Link

to verify which processors and memory modules work with your specific AA number. Can you find a barcode label

1 x PCI Express 2.0 x16 slot; some variants include additional x16 slots running in x4 mode. I/O Ports: Ethernet (RJ-45), USB 2.0 and USB 3.0 Resources for Specific Models intel desktop board 21 b6 e1 e2 specification link

According to Intel's website, the Intel Desktop Board D21-B6-E1-E2 is a server board, not a typical desktop board, and it's part of the Intel S1200BT family. to verify which processors and memory modules work