Add Four RS232 Serial Ports to an Embedded System through a mini PCI Express Slot. The MPEX4S952 4-Port RS232 Mini PCI Express Serial Card (16650 UART) turns a mini-PCIe slot into four RS232 (DB9) serial ports with data rates up to 921. 6 Kbps - a cost-saving solution for adding serial support to embedded systems missing the functionality. A native PCIe single-chip design enables you to take advantage of full PCI Express bus capability, by providing improved speed and reliability while reducing the load applied to the CPU by as much as 48% over conventional \"bridge chip\" serial cards.