The pex4s553b 4 port pci express serial card with breakout cable lets you add 4 rs232 serial ports using a single pcie expansion slot the pcie serial card includes a 1 to 4 break out cable which enables you to add 4 serial ports to a single low profile slot the serial adapter card features a native single chip design that provides optimum reliability and speed reducing the cpu load by up to 48 over conventional bridge chip serial cards a cost effective solution for connecting legacy