Hi Anna -
By default, our device drivers will enable MSI-X usage if the operating system and platform are enabled to support MSI-X. Generally speaking, most all PCI Express based motherboards can support MSI-X enabled operating systems. I cannot find a link to the S342GPV (perhaps you mean the S3420GPV) server board, but the Q57 motherboard and S3420GPV will support devices with MSI-X capabilities.
If you indicate the operating system you are using we can let you know if our driver supports MSI-X in that environment.
Thank you for using Intel Ethernet.