The 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 half heightlow profile brackets allowi