This article covers StarTech.com RS232Cシリアル2ポート増設PCIeカード 16950 UART 標準&ロープロファイルに対応 921.4kbps Windows.

Overview

The StarTech.com PEX2S953LP is a PCI Express serial card that adds two RS232C DB9 ports to any compatible desktop or server. It is designed for users who need to connect legacy serial devices—such as industrial controllers, POS peripherals, or measurement instruments—to modern PCs that lack built-in COM ports. With support for baud rates up to 921.4 Kbps and a 16950 UART featuring 128-byte FIFO buffers for both transmit and receive, this card delivers reliable, high-speed serial communication. It ships with both standard and low-profile brackets, making it suitable for full-size towers as well as small-form-factor (SFF) systems.

Connectivity & Compatibility

Interface: PCI Express 1.1 x1 (works in x1, x4, x8, x16 slots) Ports: 2x DB9 male connectors OS support: Windows 11/10/8/7, Windows Server, Linux (kernel 2.6.x and later) Data bits: 5, 6, 7, 8, 9 Flow control: Hardware (RTS/CTS), Software (XON/XOFF) External power pass-through: 5V/12V output on pin 9 when external power is connected

Product Info

Released around 2019, the PEX2S953LP typically retails for approximately ¥7,000–¥7,500. It is backed by StarTech.com's lifetime warranty and free lifetime technical support. The package includes the card, standard bracket, low-profile bracket, and a quick-install guide. This card sits in the mid-range segment of serial expansion cards. The 16950 UART provides significantly larger FIFO buffers than older 16550-based cards, reducing the risk of data loss at high baud rates. The Asix AX99100 chipset ensures broad driver compatibility across Windows and Linux.

Best Use Cases

Industrial and laboratory technicians: Ideal for connecting PLCs, CNC machines, oscilloscopes, and other RS232-equipped instruments to a modern PC. Two ports allow simultaneous control of multiple devices without needing a separate USB-to-serial adapter for each. Retail and POS operators: Perfect for integrating barcode scanners, receipt printers, and cash drawers into a single system. The low-profile bracket option makes it easy to install in compact POS chassis. * Users maintaining legacy hardware: For older modems, serial mice, or proprietary industrial terminals that behave unreliably with USB-to-serial adapters, this card provides native COM ports with stable, predictable performance.

Things to Consider

The card requires a free PCI Express slot. Most modern motherboards still include at least one PCIe slot, but it is worth checking physical clearance, especially in SFF builds where the low-profile bracket is essential. While the card supports up to 921.4 Kbps, the connected device must also support that baud rate. For typical legacy peripherals operating at 115.2 Kbps or lower, the card will automatically negotiate the correct speed. * Driver installation is generally automatic on Windows via Windows Update. On Linux, the Asix AX99100 is supported by the kernel's serial driver, though some distributions may require manual module loading. No additional third-party drivers are needed.

Product Disclosure (Amazon)

  • Manufacturer: StarTech.com(スターテック)
  • Seller: Startech Japan KK
  • Fulfilled by: Amazon
  • ASIN: B07Q8TJ2JC
  • Note: This article covers a manufacturer-made product based on Amazon listing details.