4 Port RS232 PCI Express Serial Card w/ Breakout Cable.The PEX4S552B Serial PCI Express card lets you add four RS232 serial ports using a single PCIe expansion slot. The serial card features a native single chip design that provides optimum reliability and speed, while reducing the CPU load by as much as 48% over conventional serial cards that utilize a "bridge chip" for communication with the host PCI Express bus - a cost-effective solution for connecting legacy serial devices to modern PCIe-enabled computers. The x1 PCI Express Multiport Serial Adapter Card includes a full profile and low profile bracket to ensure compatibility with both standard and small form factor computers, and is compatible with a broad range of operating systems, including Windows 2000/XP/2003/Vista, Linux Kernel 2.6.11 and up, as well as MAC OS 10.4 and above.