The PEX2S553LP low profile/half-height PCI Express Serial Card turns a PCI Express slot into two RS232 (DB9) serial connections. The card is constructed using a native single chip design that lets you harness the full capability offered by PCI Express (PCIe), while reducing the load applied to the CPU by as much as 48% over conventional bridge chip serial cards. The PCI Express RS232 Serial Adapter Card is compatible with a broad range of operating systems, including Windows®, and Linux Kernel 2.6.11 to 4.11.x, and ships with a low profile/half-height bracket installed but includes an optional full profile bracket that lets you add 2 serial ports to virtually any computer (regardless of the case form factor). This product is a replacement for our PEX2S552LP card. Backed by a StarTech.com 2-year warranty and free lifetime technical support. More from the Manufacturer

• One high speed RS232 serial port with data transfer rate up to 460.8 Kbps
• Ships with half-height/low profile mounting bracket, includes optional standard profile bracket
• Single chip design optimizes speed and reliability
• Native single-chip, single lane PCI Express
• Selectable power output on pin 9 for the serial port
• Compliant with PCI Express base specifications revision 1.1a
• Automated out-of-band flow control using CTS/RTS and DSR/DTR
• Automated in-band software flow control using programmable Xon/Xoff in both directions
• 128-byte deep FIFO per transmitter and receiver