StarTech.com 2S1P Native PCI Express Parallel Serial Combo Card with 16550 UART 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® 2000/XP/2003/Vista™/Windows 7/Server 2008 R2 (32 and 64-bit) Linux Kernel 2.6.11 and up and 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..