Question On board / off board com ports

[bwaii]

My neighbor has an analysis device that has a serial interface. The Tech says it will only work on PC's with on-board serial ports. Not PCI expansion slots. This makes computer replacement difficult. What's the difference driver-wise or architecturally? Could there be a work-around? PCI-e?

 

[bwaii]

Interestingly, it's not even all MoBos. The company rep says he has to test them one by one. I saw on this group a comment that some LANs are just PCI chips soldered on and some are hardwired directly. Could the same be for COM ports?