Add 4 RS232 serial ports to any PC using a single PCI Express expansion slot - pci express serial card - pci-e serial card - pci express RS232 - rs232 card - pci serial adapter
Add two RS232, and two RS422/485 serial ports to your PC through a PCI-Express expansion slot - pcie rs485 - pci express rs485 - pcie rs485 - pci express rs422 - pcie rs422