I've SR1630HGP server with S3420GPLC motherboard which have PCI Express 2.0 sockets. Also we've got Intel® PRO/1000 PT Quad Port Server Adapter which is PCI Express 1.0a.
The NIC is not being started/visible by OS (Linux lspci). I was unable to find the compatibility information in the net besides that PCI-e 1.1 card would work in PCI-e 2.0 socket.
So the question is: are those two compatible? Why? If yes, how to get them be friends?
To add further:
After reading motherboard manual I've discovered that the board have one PCI-E 1.0 socket and the card has started in it (inserted with no 1U chasis cover placed). This fact didn't helped because there is no raiser card for that socket for that 1U server.
So the answer discovered in experimental way is: not compatible. But more info from experts on compatibility of different versions of PCI-E is wanted, so the question remains.