Internal LVDS for between-board communicatino

Thanks for the tips. My motivation to go for LVDS stems from electrical requirements, and not particularly speed. The two cards' digital grounds are not shorted together, and differential is the best way I can see to transfer data between them.

Therefore, I think I'll still go for LVDS, low speed nonwithstanding (unless there are better options you can suggest). The choice is now between internal Stratix II LVDS and an external RXTX LVDS device.

I'll go for source-synchronous for sure, because there's no way to share a clock between the cards. When using the internal LVDS, is it completely transparent to top level code, i.e. does the corresponding Altera megafunction just present a "data_out" signal, that will come out as differential from 2 pins ?

Also, if my clock speed is 40 MHz, and the transmission rate is also 40 MHz, I guess I"ll must use a DPA at the receiving end to shift the clock by 180 degrees ? Or is it better to multiply ?