The PEX2S5531P 2S1P PCI Express card turns a PCI Express slot into two RS232 (DB9) serial ports & one parallel port. The adapter card features a native PCI Express single chip design that means that you can take advantage of full PCI Express capability, providing enhanced speed & 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 2000/XP/2003/ Vista/ Windows 7/ Server 2008 R2 (32 & 64-bit), Linux Kernel 2.6.11 & up, & MAC OS 10.4, this 2 port serial 1 port parallel PCI-Express card also features an optional low profile/half-height bracket that allows the card to be installed in virtually any computer case, regardless of the case form factor. This product is a replacement for the PEX2S5521P card.