4-port PCI Express RS232 Serial Adapter Card - PCIe RS232 Serial Host Controller Card - PCIe to Serial DB9 - 16950 UART - Low Profile Expansion Card - Windows/Linux

PCI Express to Serial Adapter | 921.6Kbps | Windows® and Linux® Compatible

Product ID: PEX4S953LP

1 stars (1 reviews) |
  • 4 PORT SERIAL CARD: Serial controller card w/16950 UART based on ASIX AX99100, allows 4x DB9 ports w/bi-directional RS232 speeds up to 921.6Kbps per port, available 256 byte FIFO buffer; Upgraded version of our popular card PEX4S952LP
  • OPTIONAL CONFIGURABLE POWER: PCIe multiport serial card provides 12v, 5v, or none through pin 9 w/up to 2A total; Each of the 4 ports are individually configurable; DB44 to 4x DB9 breakout cable incl
  • STANDARD PROFILE & LOW PROFILE BRACKET: PCI Express RS232 serial adapter card has low profile bracket pre-installed & 1x standard bracket incl for versatile install; Supports Windows XP and up & Linux
Your price
$3,434.75 MXN
VAT included in the price

This PCI Express RS232 serial adapter card lets you add four RS232 (DB9) serial ports to your computer through a PCI Express (PCIe) slot. The 4 port PCIe serial card enables you to interact with serial devices, such as card readers, printers, PIN pads, and modems, at speeds of up to 921.6Kbps. 

Maximum Compatibility 

With broad OS support, including for Windows and Linux, this PCI E serial card is easy to integrate into mixed environments. The card comes pre-configured with low-profile brackets and includes optional full-profile brackets, so installation is easy regardless of the case form factor. This card is a direct replacement for PEX4S952LP.  

Experience Optimal Technology 

  • This PCIe to serial adapter supports the following features: 
  • Compatible with industry-standard 16950 UART 
  • Supports max baud rate of up-to 921.6Kbps 
  • Provides 5/12V power output on Pin 9 when external power is connected 
  • 256-byte depth FIFO cache per transmitter and receiver 
  • Supports 9, 8, 7, 6, 5 data bits (one per port) 
  • Asix AX99100 chipset 

PCI Express 1.1 compliant 

The Choice of IT Pros Since 1985    

StarTech.com conducts thorough compatibility and performance testing on all our products to ensure we are meeting or exceeding industry standards and providing high-quality products to IT Professionals. Our local StarTech.com Technical Advisors have broad product expertise and work directly with our StarTech.com Engineers to provide support for our customers both pre and post-sales.  

PEX4S03LP is backed by a StarTech.com lifetime warranty and free lifetime technical support. 

The StarTech.com Advantage

  • Install in home or office workstations
  • Connect to automated self-service kiosks or ATM machines
  • Connect in retail POS applications
  • Connect serial printers and other legacy devices to modern computers

Partner Numbers

  • Ingram Mexico A8402QJ
  • UPC 065030887052


  • Windows 8 logo
  • Windows Server 2012 logo
  • Linux logo
  • Windows 7 logo
  • Windows Server 2016 logo
  • Windows 10 logo
  • Windows 11 logo
Windows® 7, 8, 8.1, 10, 11
Windows Server® 2003, 2008 R2, 2012, 2012 R2, 2016
Linux 2.4.x to 2.6.x LTS Versions only


Warranty Information Warranty Lifetime
Connector(s) 1 - Connector Type(s) PCI Express x1
1 - Internal Ports LP4 (4 pin; Large Drive Power)
4 - External Ports DB-9 (9 pin, D-Sub)
Environmental Operating Temperature -10°C to 80°C (14°F to 176°F)
Storage Temperature -20°C to 100°C (-4°F to 212°F)
Humidity 5~85% RH
Hardware Ports 4
Interface Serial
Bus Type PCI Express
Card Type Standard Profile (LP bracket incl.)
Port Style Integrated on Card
Chipset ID Asix AX99100
Packaging Information Package Height 2.0 in [51.0 mm]
Package Length 5.9 in [149.0 mm]
Shipping (Package) Weight 13.1 oz [370.0 g]
Package Width 8.4 in [213.0 mm]
Performance Serial Protocol RS-232
Max Baud Rate 921.6 Kbps
Data Bits 5, 6, 7, 8, 9
FIFO 256 Bytes
Flow Control None, Xon/Xoff, RTS/CTS
Parity None, Odd, Even, Space, Mark
Stop Bits 1, 1.5, 2
MTBF 214,358 hours
Physical Characteristics Product Height 0.7 in [1.8 cm]
Product Length 2.5 in [6.3 cm]
Weight of Product 9.3 oz [264.0 g]
Product Width 3.0 in [7.5 cm]
Color Green
Material Steel
Cable Length 11.8 in [30 cm]
Software OS Compatibility Windows® 7, 8, 8.1, 10, 11
Windows Server® 2003, 2008 R2, 2012, 2012 R2, 2016
Linux 2.4.x to 2.6.x LTS Versions only
Microsoft WHQL Certified Yes
Special Notes / Requirements Note Selectable power output on pin 9 of the serial port
What's in the Box 1 - Included in Package 4-Port Low Profile Serial Card
12 in [30 cm] 4-Port DB44 to DB9 Break-out Cable
Low Profile Bracket (Installed)
Full Profile Bracket
Quick-Start Guide



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Frequently Asked Questions


Older applications that use serial communication often use legacy hardware addresses that do not work with PCI, PCIe, or USB to Serial products. We recommend contacting the software provider/support team to check if this is the case.

Compliance and safety

Compliance letters

Safety Measures

  • If product has an exposed circuit board, do not touch the product under power.
  • If Class 1 Laser Product. Laser radiation is present when the system is open.
  • Wiring terminations should not be made with the product and/or electric lines under power.
  • Product installation and/or mounting should be completed by a certified professional as per the local safety and building code guidelines.
  • Cables (including power and charging cables) should be placed and routed to avoid creating electric, tripping or safety hazards.
*Product appearance and specifications are subject to change without notice.

Customer Reviews

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1 - 1 of 1 Reviews
(1 Stars)

NOT Linux compatible

By: AMAA - 06/30/2021
Normal Linux distros don't have the driver built in. The driver they supply must be built on your machine, and won't build on any recent Linux release. The driver is ancient, doesn't compile, is broken and looks like it was written by an amateur. It's totally useless and they should stop claiming that it's supported by Linux.
| Helpful?
Dan, Customer Support on 7/2/2021 7:24:57 AM
Thank you for taking the time to write a review on our serial card, and we would like to apologize for any confusion. The PEX4S953LP is only supported in Linux Kernels 2.4.x to 2.6.x LTS Versions only. If you are having issues compiling the drivers, or using the card in that Kernel, please don't hesitate to contact our support directly and we will be happy to assist from there.
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