4 Port Native PCIE RS232 Serial CardThe PEX4S553 4 Port Native PCI Express RS232 Serial Adapter Card with 16550 UART lets you add 4 RS232 (DB9) serial ports, using a single PCI Express expansion slot. Based on a native single chip design, this 4 port serial adapter card allows you to harness the full capability offered by PCI Express (PCIe), while reducing the load applied to the CPU by as much as 48% over conventional bridge chip serial cards. The RS232 Serial Adapter Card includes 4