The pex2s5531p 2s1p pci express card turns a pci express slot into two rs232 db9 serial ports and one parallel port the adapter card features a native pci express single chip design that allows you to take advantage of full pci express capability providing improved speed and reliability while reducing the load applied to the cpu by as much as 48 over conventional serial cards which use a bridge chip design compatible with a broad range of operating systems including windows 2000xp2003