Startechcom 2 port pci express pcie to rs 232 serial cards startechcom pex2s553 the startechcom pex2s553 pci express serial card lets you turn a pci express slot into 2 x rs 232 db9 serial ports based on a native single chip design no bridge chip this 2 port serial adaptor card allows you to harness the full capability offered by pci express pcie and reduces the load applied to the cpu by as much as 48 over conventional serial cards the rs 232 adaptor card is compatible with a b